TexasPeanut

ProductionGuide

B-151404-01

Contributors

Robert G. Lemon,Associate Professor and Extension Agronomist, Editor

Thomas A. “Chip” Lee,Professor and Extension Plant Pathologist

Mark Black,Associate Professor and Extension Plant Pathologist

W. James Grichar,Research Scientist

Todd Baughman,Assistant Professor and Extension Agronomist

Peter Dotray,Associate Professor and Extension Weed Scientist

Calvin Trostle,Assistant Professor and Extension Agronomist

Mark McFarland,Associate Professor and Extension Soil Fertility Specialist

Paul BaumannProfessor and Extension Weed Specialist

Clyde Crumley,Extension Agent-Integrated Pest Management

J. Scott Russell,Extension Agent-Integrated Pest Management

Gale Norman,Assistant Editor and Extension Communications Specialist

The Texas A&M University System

Contents

Introduction ....................................................................1

Agronomic Practices ........................................................1

Variety Selection ............................................................10

Plant Growth and Development......................................17

Irrigation Management ..................................................23

Weed Management ........................................................29

Disease and Nematode Management ..............................48

Insect Management ........................................................66

Application Techniques ..................................................75

Tables

Table 1. Peanut Production in Texas, 1999 ........................1

Table 2. Effect of Rotation Length on Peanut Yields..........2

Table 3. Suggested Rates of Limestone ..............................6

Table 4. Relationship Between Harvest, Yield and Grade ..........................................................22

Table 5. Critical Values for Salts in Irrigation Water for Peanuts ........................................25

Table 6. Plant Development and Water Use ....................26

Table 7. Effect of Moisture Stress on Yield......................26

Table 8. Preplant Soil Incorporated Products ..................34

Table 9. Preemergence Products ....................................36

Table 10. Postemergence Products ..................................38

Table 11. Products, Formulations and Common Names of Herbicides ....................................44

Table 12. Weed/Herbicide Response Ratings....................46

Table 13. Peanut Seed Treatment Fungicides ..................60

Table 14. Peanut Foliar Fungicides Labeledfor Use in Texas ..........................................................61

Table 15. Peanut Soil Fungicides Labeled for Use in Texas ..........................................................62

Table 16. Peanut Nematicides Labeled for Use in Texas ..........................................................63

Table 17. Reactions of Texas Peanut Varieties To Plant Diseases ..........................................64

Table 18. Insecticides for Thrips Control ........................69

Table 19. Insecticides and Rates for Lesser Cornstalk Borer Control ....................................71

Table 20. Insects Causing Foliage Damage ......................72

Table 21. Insecticides and Rates for Burrowing Bug Control ................................................73

Table 22. Insecticides and Rates Controlling Spider Mites and Southern Corn Rootworms..........................................................74

Figures*

Figure 1. Peanut growth habit ........................................19

Figure 2. The peanut flower............................................19

Figure 3. Peg growth and development............................20

*Used with permission from Cooperative Extension Service/TheUniversity of Georgia College of Agriculture/Athens

Introduction

Texas ranks second in U.S. peanut production with anannual planted acreage of 320,000 to 370,000 acres. Texaspossesses the soils, irrigation, climate and producer interestneeded for the production of all four peanut market typesrunner, Virginia, Spanish and Valencia. Each market typehas different end-use qualities and manufacturer applica-tions.

Production has been similar over the past few years (Table1). Texas produces considerable acreage of additional (con-tract) peanuts, primarily in the western region of the state.Additional peanuts generally account for about 50 percentof total statewide production.

Agronomic Practices

Crop RotationCrop rotation is the key to profitable peanut production.Peanuts should be planted in the same field only 1 year outof 3 or, in the best case, 1 year out of 4. There are numer-ous advantages to crop rotation, including improved soilfertility, reduced disease and nematode problems and moremanageable weed control systems. Recommended rotational

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Table 1. Peanut Production in Texas, 1999

% of TotalMarket Harvested Production % of Total Harvested Type Acres (tons) Production Acres

Runner 271,140 363,233 79 79

Virginia 37,147 68,324 15 11

Spanish 31,704 21,859 5 9

Valencia 2,802 3,991 1 1

Total 342,793 457,407

crops include, but are not limited to corn, grain and foragesorghums, grass sod, small grains, sesame and cotton.Longer rotations result in greater benefits, especially whendealing with disease and nematode problems. More effi-cient weed control occurs because many weeds difficult tocontrol in the peanut crop are easily controlled in the rota-tion crop. Better weed control leads to reduced foreignmaterial problems at market.

With proper rotation and in-season management, excellentyields can be attained. However, without crop rotation,peanuts will not be a profitable commodity.

Inoculation with RhizobiaPeanuts grow in a symbiotic relationship with rhizobiumbacteria—the rhizobia obtain nutrition from the plant andthe plant gains usable nitrogen from the bacteria. This isthe nitrogen fixation process. With proper seed inoculationusing a peanut-specific inoculant, a peanut crop requires lit-tle supplemental nitrogen fertilizer. Some reports suggeststhat native rhizobium strains are adequate to nodulatepeanuts. However, in western Texas, soil observations sug-gest that effective rhizobium inoculation and nodulation areessential to reach yield potential. For example, in 1999 inone West Texas field, plants averaged 12 nodules in one rowof peanuts where inoculant mistakenly was not applied. Inadjacent inoculated rows, there were 40 to 170 nodules perplant. Typically, 25 to 100 nodules per plant are observed.Also, in West Texas, volunteer peanuts the following year

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Table 2. Effect of Rotation Length on Peanut Yields

Crop (yield in lbs./acre)Rotation Length Corn Soybean Cotton

1 Year 3,457 3,360 3,150

2 Years 3,753 3,553 3,373

3 Years 4,268 3,684 4,229

Nonrotated peanuts had 3-year average of 2,840 lbs./acre.R.A. Flowers, University of Georgia, Unpublished.

exhibited little if any nodulation, which suggests thatsandy, dry soils low in organic matter do not support rhizo-bium carryover to subsequent peanut crops.

Choosing an InoculantSeveral types of peanut-specific inoculants are available.Moving across the spectrum of inoculants from seedboxpowders to granular to liquid to the new “frozen” concen-trate (a liquid delivered in frozen form to preserve integri-ty), the number of rhizobium bacteria delivered to the seedincreases. Farmers should factor in costs of inoculant, par-ticularly the cost per numbers of rhizobia. Liquid inoculantsare currently the most popular and usually promote goodnodulation. Seedbox treatments are most prone to failure asmany do not have a sticker to adhere the inoculum to theseed, and should be used only if other options are not avail-able. Hot soil temperature and low soil moisture can killrhizobia and deplete the population available for developingpeanut seedlings. For these conditions (including delayedirrigation for several days) or where adverse conditions areanticipated such as acidity or very high pH, inoculant com-panies suggest granular inoculant. Granules help buffer rhizobia from adverse conditions and help ensure survival.

Also, with increased use of liquid inoculants, the issue ofcompatibility of inoculum with seed, fertilizer, and otherchemical treatments exists. In general, insecticides are moretoxic than fungicides, which are more toxic than herbicides.Tank mixes of some chemicals (e.g., Ridomil 2E) are toxic torhizobia. If tank mixes are used, consult the inoculant’scompany representative or literature to ensure compatibili-ty. Granular inoculants generally do not have a compatabili-ty problem.

Common Inoculation MistakesRhizobium inoculant is a live bacteria! It must be cared forto preserve integrity. Avoid the following common mistakes.Do not expose to temperature above 90 degrees F. Do notstore inoculant in a building where it can get hot in theafternoon. Do not keep inoculant in the pickup cab once inthe field. This reduces rhizobium numbers. If using a liquid

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inoculant, avoid chlorinated water. Make sure that the gran-ular or liquid inoculant is placed in the seed furrow andcheck hoses for obstructions such as dirt, spider webs, etc.Always calibrate the granular boxes or liquid delivery sys-tem to ensure proper rates. Consult pesticide labels for anyincompatibility with pesticide treatments. Do not placelarge amounts of nitrogen fertilizer near the seed because itwill greatly curtail nodulation. Do not use old, expiredinoculum.

Crop Scouting: Examine Roots forNodulationFour to 6 weeks after planting use a shovel to dig (don’tpull) plants to evaluate nodulation. Nodule mass is moreimportant than number of nodules. Slice open several nod-ules. Active nodules are pink to dark red inside. If nodulesare white inside they are not yet active so check again inanother week for reddish color. Older, inactive nodules aregray or greenish inside. If nodulation is judged poor, littlecan be done to increase nodulation. Determine why nodula-tion may be poor (see the above mistakes). Minimal ornonexistant rhizobium nodulation indicates supplementalnitrogen is needed to achieve desired yields, thus nitrogenfertilizer should be considered. Poor nodulation appears tobe somewhat correlated with caliche soils, where pHgreater than 8.0 may curtail rhizobium effectiveness.

Soil Fertility and Plant Nutrition A major benefit of an effective crop rotation program is thatpeanuts respond better to residual soil fertility than todirect fertilizer applications. For this reason, the fertilizationpractices for the crop immediately preceding peanuts areextremely important. A uniform, high fertility level must bedeveloped throughout the root zone. This is best achievedby fertilizing the previous crop. If a soil test indicates theneed for fertilizer, apply it before preparing the land. Theprimary tillage operations will distribute the fertilizerthroughout the root zone.

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The following practices will ensure a strong fertility pro-gram:

A. Where soils are low in pH, soil test in the fall and applysufficient lime to raise soil pH to 6.0 to 6.5. Do not over-lime a pH higher than 7.5 because this reduces theplant’s ability to absorb other nutrients, especiallymicronutrients. In addition, this pH range is optimumfor effective rhizobium nodulation and nitrogen fixation.

B. Use a balanced fertility program based on soil testingthat maintains adequate levels of phosphorus, potassi-um, calcium, magnesium and micronutrients.

C. Avoid high levels of potassium fertilizer in the upper 4inches of soil. This can lead to increased incidence ofunfilled pods (pops) and pod rot that will affect peanutquality and yield. This may be of particular concern inWest Texas cotton/peanut rotations where soil potassiumis already high.

D. Monitor the pegging and fruiting zone for calcium. Alack of calcium can lead to empty pods and darkenedplumules in seed (concealed damage), poor germinationand potentially increased risk of aflatoxin when soil con-ditions are favorable for Aspergillus flavus mold develop-ment. Adequate calcium must be available in the peg-ging zone during seed and pod development (see Table3).

E. Peanuts are efficient legumes that synthesize their ownnitrogen requirements through association with specificrhizobium soil bacteria that are already present in manypeanut soils. However, if peanuts have not been grownin a specific soil during the past 4 or 5 years, the cropshould be inoculated at planting with a peanut-specificcommercial inoculant. In West Texas, rhizobium inocula-tion is strongly recommended for every peanut crop.

F. Soil test and accumulate a history of soil nutrient levelsin your cropping systems. Tracking your field’s fertilityhistory can help avoid overlooking potential soil fertilityproblems that can lead to reduced yields and inferiorquality peanuts.

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Nitrogen, Phosphorus and PotassiumOne of the major benefits of producing peanuts, or anylegume, is that the crop requires little nitrogen fertilizer.Texas research on response of peanuts to nitrogen fertilizerreveals that, in general, no response is observed in Southand Central Texas provided the crop is properly nodulated.In West Texas several experiments have looked at starternitrogen, preplant nitrogen, and midseason nitrogen appli-cations. Although in some tests small yield increases mayhave been observed for large nitrogen applications, therehas been no consistent trend toward higher yields withnitrogen additions. Soil nitrate levels (including subsoilnitrate) and degree of rhizobium nodulation may affectnitrogen results, but these two factors have not been evalu-ated in experiments. Starter nitrogen rates up to 30 poundsnitrogen per acre should not negatively influence noduleformation. The practice of putting out nitrogen in smallincrements through the center pivot is now being evaluat-ed. Late-season nitrogen applications should be avoided todiscourage soil-borne diseases and delayed maturity, partic-ularly in West Texas.

For the most efficient use of phosphorus and potassium fer-tilizers, apply them to the previous crop or before landpreparation, and thoroughly incorporate them into the root

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Table 3. Suggested Rates of Limestone1 (tons/acre)

Soil TextureSand and Sandy loams

Soil pH range loamy sands and loams

6.0 to 6.42 13 1

5.6 to 5.9 1 11/2

Below 5.6 2 3

1Use dolomitic limestone if low magnesium levels are indicated by soil test.2For soils with a pH greater than 6.4 and high calcium levels but low-to-medium magnesium

levels, consider applying 150 lbs. per acre of potassium magnesium sulfate broadcast.3For very sandy soils with a pH of 6.0 or more, gypsum is suggested if the soil calcium level

is low.

zone. Always follow soil test recommendations to avoidover- or underfertilizing the crop. This is especially impor-tant for potassium, because high levels in the pegging zonehave been found to interfere with calcium uptake and toincrease the incidence of pod rotting organisms such asPythium and Rhizoctonia.

CalciumIn runner and Virginia type peanuts calcium is by far themost critical nutrient for achieving high yields and grades.Low levels of calcium cause several serious productionproblems, including unfilled pods (pops), darkenedplumules in the seed and poor germination. In fields low incalcium and high in sodium, a condition called pod rot iscommon. Supplying gypsum or a liquid form of calciumcan help alleviate these problems.

Calcium must be available for both vegetative and poddevelopment. Calcium moves upward in the plant in thexylem tissues. It does not move downward in the phloem.Therefore, calcium is not transported from leaves to pegsand to the developing pods. Pegs and pods absorb calciumdirectly from the soil solution, therefore calcium must bereadily available in the pegging zone. Foliar applied calciumtreatments do not correct calcium deficiencies.

On soils with pH 6.0 or greater, calcium fertilization isaccomplished with agricultural gypsum (CaSO4) or calciumin liquid form. Calcium contained in gypsum and certainliquid calcium products is relatively water soluble andenters into soil solution. Experience in Texas indicates thata soil test level of 600 ppm calcium is adequate for peanutproduction. If soil calcium levels are less than 600 ppm, orif irrigation water is saline, gypsum applications may beneeded. In West Texas, gypsum is prohibitively expensivedue to transportation costs, but all West Texas soils test highin calcium. The effect on peanut yield and quality of liquidcalcium products applied midseason through the pivot isunknown.

Gypsum should not be applied during land preparation orbefore planting because it can be leached below the pegging

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zone. Best results have been obtained when gypsum isapplied at initial flowering. Banded applications over therow (12- to 16-inch band) of 600 pounds gypsum per acreand broadcast applications of 1,500 pounds per acre haveproven to be adequate. Rainfall or irrigation after applica-tion is needed to move the gypsum into the pod develop-ment zone.

Micronutrients Micronutrients include zinc, iron, manganese, copper,boron and molybdenum. As soil pH increases, micronutri-ent availability decreases. Therefore, high pH soils are moreprone to micronutrient problems. Late-season foliar applica-tions of micronutrient fertilizers seldom result in economicreturns.

Zinc—Do not band zinc near seed since stand losses canoccur. If soils are acid, a zinc application may not be neces-sary since zinc response on acid soils is seldom observed.Alkaline soils with a high soil phosphorus-to-zinc ratio mayrequire zinc even though the zinc tests are high. Deficiencysymptoms include interveinal chlorosis of the youngestleaflets and, in severe situations, stunted plants and slowdevelopment of new leaves. If soil-applied zinc fertilizerproducts are used, consider highly soluble zinc sulfatemonohydrate. Chelated zinc forms are also available, butcompare their costs to traditional zinc sulfate at 2 to 4pounds zinc per acre.

Iron—A deficiency of available iron in soils above pH 7.0can cause severe chlorosis or yellowing of leaves and reduc-tion in yield. Generally, soil applications of iron materialsare ineffective or uneconomical and foliar spray applica-tions are suggested. Applications may need to be repeatedat 10-day intervals if problems are severe. Symptoms willbe observed in the youngest leaflets, which are chlorotic topale green and develop interveinal chlorosis. Foliar ironchelates can be quite expensive. For foliar iron applicationsadequate results may be achieved by using 1 pound of ironsulfate per 5 gallons of water per acre. Use a surfactant orsticker in the spray, and ensure that nozzles produce a finespray. For young peanuts apply 5 to 10 gallons per acre and

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increase to 10 to 15 gallons per acre with subsequent appli-cations. Ground spray rigs achieve better placement of ironon the plants than aerial spray, but consider costs and time-liness of application.

Manganese—Deficiencies have been documented in SouthTexas. Manganese deficiency symptomology is similar toiron and zinc. Problem fields can be treated with foliarsprays of manganese products.

Copper—Deficiencies are often mistaken for other prob-lems. Initial symptoms include wilting of upper leaves, fol-lowed by chlorosis and leaf scorching. Dead, brown tissuedevelops from the leaf margins and progresses inward untilthe petiole drops. Flower production can be reduced, result-ing in significant yield reductions. Soil applications of cop-per are the preferred method for managing deficient fields.However, foliar spray treatments of copper sulfate or simi-lar copper-containing materials applied at early bloom cor-rect problem fields. Foliar fungicides containing copper alsomay correct the problem. Excessive amounts of copper cancause loss of root growth.

Boron—Fortunately boron deficiency problems are rare inTexas. The most significant symptom is deterioration of thecentral portion of the kernel producing a dark brown col-ored cavity known as “hollow heart.” This causes the kernelto be graded as “internal damage” and drastically lowers theselling price. If the problem is identified as a boron defi-ciency, apply 1/2 to 3/4 pound of elemental boron per acrein the fertilizer. Do not make further applications without asoil test. Boron often creates problems because the rangefrom boron deficiency to boron toxicity is narrow comparedto other nutrients. In small amounts boron can be verytoxic and injurious to plants and indiscriminate use reducesyields drastically. Check boron levels in the irrigation waterbefore applying. Amounts greater than 0.75 ppm are causefor concern as boron could accumulate, leading to borontoxicity in peanuts. Many soil tests in West Texas recom-mend boron for peanuts, but unless boron levels in irriga-tion water are known, use caution in applying boron fertil-izer apart from visible plant deficiency.

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Molybdenum—Deficiencies usually do not occur unlesssoils are highly acid. Adding limestone to raise soil pH usu-ally corrects the problem.

Variety Selection

Use high quality seed of a recommended variety. Plant atthe recommended plant population based on a given rowspacing and seed count. Consult with shellers on marketacceptance of peanut varieties.

Plant peanuts as soon as soil conditions are favorable forrapid germination and development. Late planting datesgenerally reduce yield and quality and increase the risk offreeze damage and late season drought to peanuts. In WestTexas, runner and Virginia varieties should be planted byMay 15, while Spanish should be sewn by June 1.

Prepare seed beds carefully to assure seed germination andemergence. Adjust planting depths to soil type, tempera-ture, moisture conditions and planting date. If soils areextremely dry, pre-irrigate fields to obtain favorable soilmoisture, rather than dry-planting and then irrigating. Thiswill ensure optimum stand establishment and reduce thepotential for herbicide damage.

Variety selection is one of the most important decisions agrower will make during the season. There have beennumerous varietal releases during the past 5 years andgrowers have more runner market types available than everbefore. Commercial varieties have been released that pos-sess various degrees of tolerance or resistance to numerousdiseases. Also older peanut varieties that were once tolerantto specific diseases may now be susceptible. With increasedemphasis on host plant resistance, the number and speci-ficity of varieties will continue to increase. The Texas A&Mbreeding program is addressing several production issuessuch as tomato spotted wilt virus (TSWV), root knot nema-tode, sclerotinia blight and improved oil quality (high oleicacid/linoleic acid ratio).

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Texas is much different than other peanut producing statesbecause the state can be divided into three primary produc-tion regions—south, central and west regions. The key fac-tors (soils, climate, disease, irrigation, etc.) impacting pro-duction in these areas vary considerably and as a conse-quence the best varietal choices for one area may not bewell suited for another.

About 10 commercial runner varieties are grown in Texas.In 1999, the runner market types comprising the largestpercentage of acreage were Florunner, Flavor Runner 458,Tamrun 96, Georgia Green and Tamrun 88. The west Texasregion was planted heavily to high oleic varieties in 2000,and this trend is expected to continue.

Most Virginias in Texas are contract additionals, and NC-7has been the preference of shellers for several yearsbecause of its high percentage of extra large kernels.However, several other Virginia varieties possessing greateryield potential are being evaluated to determine adaptabili-ty to the west region.

Spanish varieties currently produced are Tamspan 90 andSpanco. A high oleic Spanish variety developed by theTexas A&M University peanut breeding program should beavailable in 2002.

Several factors must be considered when deciding on vari-ety. First, it is extremely important to evaluate varietiesbased on regional performance. Certainly, yield and gradeattributes must be given top priority, but disease tolerance,growth habit, maturity, and seed quality and availabilityshould also be considered. The “perfect variety” possessingall the necessary traits for Texas’ diverse environments doesnot exist, so it makes good sense to plant a couple of differ-ent varieties to reduce the production risk.

West TexasThe west Texas region can be characterized as a high-yield-ing environment that uses center pivot irrigation and haslow disease pressure. The semiarid climate does not favorfoliar disease development in most years; however, the soil-

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borne, pod rot complex (Rhizoctonia and Pythium) is presentand can be moderate to severe in some fields. Traditionalrunner types such as Florunner and Tamrun 88 have per-formed very well in the region. However, in 2000, much ofthe acreage was planted to Flavor Runner 458 and otherhigh oleic varieties such as AT 1-1, AT 201 and Sunoleic97R. In fields that have not been properly rotated and havea history of moderate to severe pod rot problems, Tamrun96 may be a good choice. This variety, released primarilybecause of its tolerance to TSWV, also tends to suffer lessloss from pod rot problems.

Central TexasThe central Texas area is a traditional production regionand experiences most problems associated with peanut pro-duction (southern blight, pod rot complex, limb rot, leafspot, root knot nematode, sclerotinia blight). Also, TSWVbecame a problem in some portions of the region in 1996.Tamrun 96 and Georgia Green have become very popularover the past 2 years. Tamrun 96 has performed very wellunder disease and nondisease conditions. Tamrun 96 has arobust growth habit, producing very large vines, especiallyin comparison to Georgia Green, which develops a smallercanopy than other runner types.

South TexasThe south Texas region is a traditional area that has experi-enced various levels of TSWV over the past 15 years. Thepast few seasons have been characterized by reduced inci-dence of the virus and yields across the region have beenvery good. GK7 was a popular choice in the past, butTamrun 96, Georgia Green, and AT 108 have gained rapidfavor with producers. These varieties have produced highyields and grades and possess appreciable tolerance orresistance to TSWV. Tamrun 96 will show visible symptomsof TSWV, but the variety remains sturdy. To prevent lossduring the harvest season to the influences of hurricanes orother inclement weather, it is a good policy to select vari-eties that are sturdy and that have a secure peg attachment.Caution should be taken with AT 108. The variety does notpossess strong tolerance to TSWV.

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Characteristics of Runner Varieties Florunner—University of Florida release, 1969. Has hadinsurmountable influence on the peanut industry.Continues to be the standard of performance in west Texas.Produces high yields and excellent grades. Is being replacedby newer, more disease resistant varieties in most otherpeanut growing regions. Most varieties will be compared ingrowth habit and maturity to Florunner.

Georgia Green—University of Georgia release, 1995. Hasresistance to TSWV and southern blight (Sclerotium rolfsii).Maturity similar to Florunner. Vine growth is less thanother runner market types and does not show prominentmain stem as do typical runner types. Small seeded runnervariety, about 825 seed per pound. Web blotch (Didymellaarachidicola) was found on this variety in 1998 in southTexas and the Rolling Plains production regions. Good vari-ety for central and south Texas. Shows excellent responsewhen planted in twin rows.

Tamrun 96—Texas A&M University release, 1996. Goodtolerance to TSWV. Maturity similar to Florunner. Tamrun96 has performed better than most varieties in fields havingsclerotinia blight (Sclerotinia minor) problems and has sometolerance to southern blight (Sclerotium rolfsii). Very robustvine growth, especially on more fertile peanut soils.Tamrun 96 has performed very well across all Texas pro-duction regions, but especially in central and southernareas. Tamrun 96 also is a good choice for fields with podrot problems in West Texas. Very sturdy vine and pegattachment.

Virugard—AgraTech Seeds release, 1997. Possesses toler-ance to TSWV. Runner x Virginia cross. Appears to be 7 to10 days earlier than Florunner. Has a Virginia growth habit,does not show prominent main stem, very large kernel size.Late-season micronutrient deficiencies observed similar toAT 120. Growers should be aware of the earliness in thisvariety to prevent losses from over-mature pods. Pepperspot (Leptosphaerulina crassiasca) was found on this varietyin 1998 in Texas. Late-season foliar fungicide applicationsmay be warranted to maintain healthy vines.

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Florida MDR 98—Most recent release from University ofFlorida.”MDR” stands for multiple disease resistance. MDR98 has tolerance to late leafspot (Cercosporidium person-atum), southern blight (Sclerotium rolfsii), TSWV and rust(Puccinia arachidis). Most of the disease resistance derivedfrom Southern Runner, one of the parents. Like SouthernRunner, matures later than all other commercial runnervarieties ( 2 to 3 weeks). Classified as a midoleic varietywith about 65 percent oleic acid. The late maturity of thisvariety makes it questionable for Texas.

Georgia Bold—University of Georgia release, 1997. Largerkernel size than Florunner and has performed very well inTexas variety trials. Possesses moderate tolerance to TSWV.Similar maturity and growth habit to Florunner. Does notresemble Georgia Green in canopy development or kernelsize.

GK 7—AgraTech Seeds release, 1984. Agronomic character-istics similar to Florunner. Develops prominent main stem.Some tolerance to TSWV.

AT 108—AgraTech Seeds release, 1994. Similar to GK 7 ingrowth characteristics. Main stem is not as prominent asGK 7. Seed size similar to GK 7, but has higher percentageof jumbo runner grade. Matures earlier than GK 7.

AT 120—AgraTech Seeds release, 1994. Early maturing run-ner, depending on conditions may be 7 to 10 days earlierthan Florunner. Growth habit is runner plant type, withSpanish flowering habit—it flowers on the main stem.Generally produces high yields and earliness in west Texas.Develops excellent “root crop.” Initiates cutout at about 120days after planting and shows more micronutrient deficien-cy in new growth than other varieties. Growers should beaware of the early maturity and dig accordingly to avoidlosses from over-mature pods. Pepper spot (Leptosphaerulinacrassiasca) was found on this variety in 1998. Late-seasonfoliar fungicide applications may help maintain healthyvines. Black hull (Thielaviopsis basicola) has been found onthis variety in west Texas. Potential problems could occur ifthis variety is planted in cotton fields with a history ofblack root rot.

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Tamrun 88—Texas A&M University release, 1988. Verysimilar to Florunner in most agronomic characteristics.Emergence is more uniform and stand establishment morerapid than any other runner type grown in Texas—goodcharacteristic for west Texas. Extremely susceptible toTSWV. Produces excellent yields and grades in west Texas.

Okrun—Oklahoma State University and USDA-ARS release,1986. Agronomic characteristics similar to Florunner.Slightly more resistant to leaf spot and pod rot.

High Oleic VarietiesFlavor Runner 458—Mycogen release. High oleic variety.Similar to Florunner in agronomic characteristics.Performance in west Texas has been very good with highyields and grades. Slow emergence has been observed withthis variety.

GK 7 High Oleic—AgraTech Seeds release in 1997. Higholeic variety with agronomic characteristics similar to GK7. GK 7 has very prominent main stem, which aids in rowidentification.

Sunoleic 97R—University of Florida release to replaceSunoleic 95R. High oleic variety has about 80 percent oleicand 2 to 3 percent linoleic fatty acids, based on total fat/oilcontent. Yields higher than Sunoleic 95R. Does not have asmuch pod splitting as Sunoleic 95R. Yielded very well incentral and west Texas in 1997. Susceptible to TSWV.

AT 1-1—AgraTech Seeds release, 1999. Has growth habitsimilar to AT-120 and also flowers on the main stem. Sometolerance to TSWV. Appears to be about 5 to 7 days earlierthan other runner varieties. Poor yield and grades in 2000variety trails.

AT 201—AgraTech Seeds release, 1999. Similar to GK 7 inmaturity. Showed good early-season vigor in variety testsconducted in 2000. Tolerant to TSWV.

Characteristics of Virginia VarietiesNC7—Largest seeded variety released in 1978 by NorthCarolina State University. NC7 has a growth habit interme-

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diate between runner and bunch. NC7 generally gradeshigher and has a larger percentage of extra large kernelsthan other varieties. Possesses moderate resistance to earlyleafspot, but very susceptible to sclerotinia blight. Currentseed stocks contain several off-types.

NC 12C—Large seeded variety similar in maturity andplant type to NC7. Possesses moderate level of resistance toearly leafspot, but very susceptible to sclerotinia blight. NC12C has a thin hull so it should be harvested carefully toavoid excessive loose shelled kernels. In Texas variety trials,has outyielded NC7.

Gregory—Large seeded variety similar in maturity to NC7.Has growth habit intermediate between runner and bunchtypes. This variety produces a very high percentage of extralarge kernels, and has a higher calcium requirement thanNC7.

VA-98R—Has a runner growth habit and is 3 to 5 days ear-lier than NC7. Extra large kernels are lower than NC7. Hasvery good yield potential

VC-2—AgraTech Seeds release, 2000. High oleic variety.Similar to NC7 in maturity. Has shown tolerance to TSWV.

Characteristics of Spanish VarietiesTamspan 90—Texas A&M University release, 1990. TypicalSpanish growth habit. Resistant to pythium pod rot and scle-rotinia blight. Excellent yield potential. Responds well toirrigation and twin row planting patterns.

Spanco—Oklahoma State University and USDA-ARSrelease, 1981. Good yield potential, but does not possessthe pythium pod rot or sclerotinia resistance found inTamspan 90. Responds to irrigation and twin row plantingpatterns.

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Plant Growth and Development

Germination and Seedling DevelopmentThe peanut seed consists of two cotyledons (also called seedleaves) and an embryo. The embryo comprises the plumule,hypocotyl and primary root. The plumule eventuallybecomes the stems and leaves of the plant, and thehypocotyl is the white, fleshy stem located between thecotyledons and the primary root. As the seed imbibeswater, there is a resumption in metabolic activity, the seedbegins to swell, and cell division and elongation occur. Asthe embryo grows, the testa (seed coat) ruptures and theseedling emerges.

The minimum and maximum temperature requirements forpeanut seed germination are not well defined. Research hasshown that seed will germinate under a wide range of cir-cumstances (consider volunteer peanuts); however, underfield conditions the minimum average soil temperatureshould be 65 degrees F at the 4-inch depth, with a favor-able weather forecast. This ensures rapid, uniform emer-gence and reduces the risk associated with stand loss fromthe seedling disease complex.

The seedling uses food reserves from the cotyledons duringthe initial stages of growth. Under most situations, peanutsshould reach the ground cracking stage 7 to 14 days afterplanting, depending upon soil temperature. The growth rateof the hypocotyl determines how quickly the shoot willemerge from the soil. Most current commercial varietiesshow little difference in emergence rates and/or seedlingvigor. A final plant density of three to four plants per rowfoot is adequate.

Plant DevelopmentAs the plant grows, the root develops very rapidly in com-parison to the shoot. By 10 days after planting, root growthcan reach 12 inches. By 60 days, roots can extend 35 to 40inches deep. Late season measurements have found peanut

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roots down to 6 to 7 feet. Roots grow at a rate of about 1inch per day as long as soil moisture is adequate.

The hypocotyl pushes the plumule upward causing “groundcracking.” After emergence, the plumule is called a shootand consists of a main stem and two cotyledonary lateralbranches. At emergence the main stem has at least fourimmature leaves and the cotyledonary lateral brancheshave one or two leaves also. The seedling develops slowlyshowing as few as eight to 10 fully expanded leaves 3 to 4weeks after planting.

Leaves are attached to the main stem at nodes. There is adistinct pattern by which these leaves are attached. Thereare five leaves for every two rotations around the mainstem, with the first and fifth leaves located one above theother. Leaves attached to the cotyledonary laterals andother lateral branches are two-ranked, so there is one leafat each node, alternately occurring on opposite sides of thestem. Peanut leaves have four leaflets per leaf, makingthem a tetrafoliate. The leaflets are elliptical in shape andhave a prominent midvein.

The main stem and cotyledonary laterals determine thebasic branching pattern of the shoot. The main stem devel-ops first and in runner type plants the cotyledonary lateralseventually become longer than the main stem. Additionalbranches arise from nodes on the main and lateral stems.

The growth habit of peanut is described as bunch, decum-bent or runner. Spanish and Valencia market types are clas-sified as “bunch,” with their upright growth habit and flow-ering on the main stem and lateral branches. Most Virginiaand runner market types are considered to have a prostrate(flat) growth habit and do not flower on the main stem.Decumbent varieties have an intermediate growth habitbetween a runner and bunch. Several Virginia varieties areclassified as decumbent.

Peanuts are indeterminate in both vegetative and reproduc-tive development (similar to cotton). This means that theplant is producing new leaves and stems at the same timethat it is flowering, pegging and developing pods.

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Consequently, developing pods compete with vegetativecomponents for carbohydrates and nutrients. Once a heavypod-set has been established, the appearance of flowers isgreatly reduced.

BloomAbout 30 days after emergence, peanut plants begin to pro-duce flowers. Flower numbers will continue to increaseuntil the plant reaches peak bloom at about 60 to 70 daysafter emergence, and then flower development will begin todecline. High temperature, moisture stress and low humidi-ty can have a severe impact on the flowering response, lim-iting the number of flowers produced and reducing flowerpollination. Ultimately, this can result in reduced yield anddelayed pod set. However, the peanut plant can compensateto some extent by initiating a large flush of flowers whenfavorable environmental conditions return.

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Figure 1. Peanut growth habit is bunch (left), decumbent (center) orrunner (right).

Figure 2. The peanut flower.

Peanut flowers are borne in leaf axils on primary and sec-ondary branches. Several flowers can originate from eachnode, however, only about 15 to 20 percent will produce aharvestable pod. The peanut flower is a perfect flower(male and female structures present in the same flower)and is self-pollinated. It has a showy yellow bloom andwhen it first emerges, the petals are folded together. Theearly morning of the following day the petals unfold andpollen is shed. Fertilization takes place in 3 to 6 hours. Thefertilized ovary begins to elongate and grows downwardfrom the node to the soil. This specialized structure, calleda peg, becomes visible about 7 days after fertilization. Thesharp-pointed peg enters the soil about 10 to 14 days afterpollination. The developing pod is located in the tip of thepeg. Once in the soil, it begins to enlarge and forms the podand kernels. It is interesting to note that the pod will notbegin growth until the peg is in the presence of darkness.Because several flowers can develop from each node, sever-al pegs and pods can be found originating from a singlenode. The indeterminate fruiting habit of the peanut meansthe plant will have pods of varying maturity. Consequently,peanut harvest determinations are based on the presence of70 to 80 percent mature pods.

Pod and Kernel DevelopmentDuring the early stages of pod development, the tissue issoft and watery. As the pod develops, the hull and kernels

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Figure 3. Peg growth and development.

begin to differentiate. The cell layer just below the outercell layer of the pod changes from white to yellow toorange to brown to black as it matures, providing a colorindication of optimum harvest date. The inner pod tissueseparates from the seed and darkens as the seed grows andpresses against the hard layer of the hull. This is indicatedby the dark brown to black veination on the inside of thehull.

Pods attain full size about 3 to 4 weeks after the peg entersthe soil. Although the pod has reached full size, kerneldevelopment has barely begun. Mature, harvestable podsrequire 60 to 80 days of development. In Texas, a maturecrop can be produced in 130 to 140 days in south Texas,140 to 150 days in central Texas, and 150 to 170 days inwest Texas. Temperature (both day and nighttime) interactswith variety, planting date, seasonal moisture, etc., in con-trolling development of the crop. However, the controllingfactor in all plant development is temperature.

Maturity and Harvest DeterminationAs pods mature, the inside portions become brown toblack, while immature pods retain a fresh, white appear-ance. The cellular layer just below the outer layer of thepod undergoes several color changes during the maturationphase. This cellular layer is called the mesocarp. It changesin color from white to yellow to orange to brown and final-ly black as the pod matures. This color distinction can beused to estimate crop maturity with the “hull scrape”method. Hold the pod with the beak pointing down andaway from you, and with a pocket knife scrape away theouter hull in the area from the middle of the pod to the pegattachment point. This region of the pod is known as thesaddle. Pods should be moist when the color determinationsare made. To get an accurate representation of the field, col-lect three adjacent plants (about 1 foot of row) from threeto five locations in the field. As with all field assessments(soil and plant tissue testing, insect and disease scouting,etc.), the results are only as good as the collection proce-dure, so collect an adequate sample.

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Determining the optimum digging time is a crucial deci-sion for a grower! Using the calendar to predict diggingdates is a good way to lose yield, grade and money. There isno substitute for scouting fields and observing pod develop-ment, especially late in the season. The optimum time todig a peanut crop is when it has reached its peak yield andgrade. If dug too early or late, yield and crop quality will besacrificed. Because of the indeterminate fruiting habit ofthe peanut, each plant will have pods of varying maturity.Consequently, the risk of losing early-set mature pods ver-sus later-set immature pods must be considered, and a com-promise must be achieved. Runner types should be dug at70 to 80 percent maturity, Virginia types at 60 to 70 percentand Spanish and Valencia at 75 to 80 percent maturity.

Peanuts may gain from 300 to 500 pounds per acre in yieldand one to two grade points during the 10- to 14-day periodpreceding optimum digging time. Conversely, similar yieldand grade losses can occur if digging time is delayed 1 to 2weeks. Overmature and diseased plants (pod rot complex,leaf spot, southern blight, sclerotinia blight, rust, etc.) haveweakened peg attachments, resulting in significant pod lossduring digging and combining.

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Table 4. Relationship Between Harvest, Yield and Grade

Yield loss GradeDigging time (lbs./A) (Total Sound Mature Kernels)%

14 days early 740 73.9

7 days early 250 74.2

optimum —— 75.0

7 days late 500 75.6

14 days late 540 ——

Irrigation Management

Irrigation is the key to current and future peanut produc-tion in Texas. Since 1996, Texas irrigated acreage has steadi-ly increased. Irrigation ensures a stable supply of highyielding, good quality, aflatoxin-free peanuts. The total sea-sonal water requirement for maximum peanut yields isapproximately 24 to 28 inches. Water can be a scarce com-modity; consequently, producers must consider systemcapacity as a guide in determining suitable acreage forplanting. It is best to plant less acreage and irrigate ade-quately, than to plant larger acreages that are subject towater shortfalls. In addition, peanuts do not tolerate waterquality problems as well as cotton, and this becomes evi-dent in low rainfall seasons.

Irrigation Water QualitySalinity has become a problem throughout many areas ofTexas. As water quality becomes marginal and cropping pat-terns change, some areas may experience injury andreduced yields. Each crop has its own susceptibility rangeto marginal quality water. Peanuts are not very tolerant, soit is imperative that water quality be assessed before deter-mining where to plant peanuts.

Water quality is determined by the total amounts of saltsand types of salts present in the water. A salt is a combina-tion of two elements or ions, one has a positive charge(sodium) and the other has a negative charge (chloride).Water may contain a variety of salts including sodium chlo-ride, sodium sulfate, calcium chloride, calcium sulfate, mag-nesium chloride, etc.

Salty irrigation water can cause two major problems in cropproduction: salinity hazard and sodium hazard. Salts com-pete with plants for water. Even if a saline soil is water sat-urated, the roots are unable to absorb the water and plantswill show signs of stress. Foliar applications of salty watercommonly cause marginal leaf burn and in severe cases canlead to premature defoliation and yield and quality loss.

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Sodium hazard is caused by high levels of sodium that canbe toxic to plants and can damage medium and fine-tex-tured soils. When the sodium level in a soil becomes high,the soil will lose its structure, become dense and form hardcrusts on the surface. To evaluate water quality, a watersample should be analyzed for total soluble salts, sodiumhazard and toxic ions.

Total soluble salts analysis measures salinity hazard byestimating the combined effects of all the different salts inthe water. It is measured as the electrical conductivity (EC)of the water. Salty water carries an electrical current betterthan pure water, and EC increases as the amount of saltincreases.

Sodium hazard is based on a calculation of the sodiumadsorption ratio (SAR). This measurement is important todetermine if sodium levels are high enough to damage thesoil or if the concentration is great enough to reduce plantgrowth. Sometimes a factor called the exchangeable sodiumpercentage may be listed or discussed on a water test; how-ever, this is actually a measurement of soil salinity, notwater quality.

Toxic ions include elements like chloride, sulfate, sodiumand boron. Sometimes, even though the salt level is notexcessive, one or more of these elements may become toxicto plants. Many plants are particularly sensitive to boron.In general, it is best to request a water analysis that liststhe concentrations of all major cations (calcium, magne-sium, sodium, potassium) and anions (chloride, sulfate,nitrate, boron) so that the levels of all elements can be thor-oughly evaluated.

Water Quality, Yield RelationshipsThe critical level of boron in irrigation water for cotton andgrain sorghum is 3 ppm. Preliminary survey studies con-ducted over the past 2 years indicate that peanuts are muchmore susceptible to high boron concentrations. Boron levelsgreater than 0.75 ppm in water can cause severe yieldreductions. This concentration should be viewed as the crit-ical threshold level for irrigation systems used for peanuts.

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Also, the sodium adsorption ratio (SAR) has been found tocorrelate with reduced peanut yields. The critical SARvalue for cotton, grain sorghum and corn is 10. However,peanuts are much more sensitive to SAR values in therange of 5 to 7. Yield reductions associated with this rangeindicate that the critical threshold level for peanuts is muchlower.

Water Quality, Grade RelationshipsPeanut grades can be reduced with increasing chlorides andtotal soluble salt (EC) concentrations in irrigation water.Study results point to a critical threshold for EC of 2,100 to2,500 umhos/cm and 400 ppm chloride. Grade reductionsassociated with increasing salinity may be related toreduced calcium uptake by kernels caused by antagonisticinteractions with sodium, chloride, magnesium and potassi-um.

Irrigation and Water Use The growing season for peanuts can be divided into threedistinct phases—prebloom/bloom, pegging/pod set and ker-nel fill/maturity. Water use will vary with these develop-mental stages. In general, water use is low in the early sea-son, but during the reproductive period water consumptionis at its peak. Consumption declines as pods begin tomature. Specifically, water use can be categorized as fol-lows:

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Table 5. Critical Values for Salts in Irrigation Water for Peanuts

Measurement Critical Value for Peanuts

Total Dissolved Salts (EC) 2100 umhos/cm = 2.1 mmhos/cm = 1344 ppm

Sodium Adsorption Ratio (SAR) 5-to-7

Boron 0.75 ppm

Chloride 400 ppm

Sodium 400 ppm

R.G. Lemon and M.L. McFarland, Texas Agricultural Extension Service, College Station, TX

Research conducted in Georgia demonstrated how moisturestress at various periods during the season can affect pro-duction.

During the bloom period, water stress can delay formationof flowers, or under extreme conditions flowering can becompletely inhibited. In Texas, it’s not a matter of if therewill be extreme heat and moisture stress, it’s just a questionof when and for how long a duration. Even with irrigation,these climatic factors can be very difficult to overcome.

Peanuts are of tropical ancestry and do well at moderatelywarm temperatures. Temperature has a direct influence ongrowth and development of the crop through its effects onphotosynthesis and flower set. The optimum temperaturefor peanut growth and development is about 86 degrees F.

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Table 6. Plant Development and Water Use

Stage of Development Water Use

Germination and seedling establishment very high

Vegetative growth low to moderate

Flowering and pegging very high

Pod development very high

Kernel development high

Maturity moderate

Table 7. Effect of Moisture Stress on Yield

Stress Period (days after planting) Yield (lbs./A)

30 to 65 3,960

65 to 100 2,900

100 to 135 4,120

Optimum moisture 4,540

C.K. Kvien, Coastal Plain Experiment Station, Tifton, Georgia, 1987-1988.

Very high temperatures slow down the crop growth rate.Even in conditions of adequate water, temperatures above95 degrees F can impair development of the crop. Researchhas shown that photosynthetic activity can be reduced byas much as 25 percent at temperatures above 100 degrees F.

Peanuts have a higher rate of flower and fruit set and betterpod development at temperatures less than 90 degrees F.High temperatures, occurring both day and night, canreduce flower set. Research has shown that the optimumtemperature for flowering and peg set ranges between 68degrees F to 80 degrees F. An exposed sandy soil can getvery, very hot, thus affecting flower set. High temperaturesreduce the number of flowers produced, and when coupledwith low humidity, flowers may not pollinate well. Underhot and dry conditions, flower structures may not developproperly, resulting in poor fertilization. Fortunately, thepeanut plant can compensate by developing a large flush offlowers when the environmental conditions become morefavorable. Crop canopy closure reduces temperatures andincreases humidity in the canopy, creating a more favorableenvironment for flowering, pegging and pod development.Also, as plants become older they become less sensitive tostress.

After bloom, peg penetration into the soil requires adequatemoisture. Once active pegging and pod formation havebegun, it is recommended that the pegging zone be keptmoist, even if adequate moisture is present in the soil pro-file. A moist pegging zone aids the uptake of calcium by thepods. Failure of pegs to penetrate soil and develop pods canresult from low relative humidity and high soil tempera-tures. Therefore, it is extremely important to supply addi-tional moisture during pegging, even if soil moisture is ade-quate.

In-Season Irrigation ManagementEvery producer has his own ideas about and methods forwatering a crop; often what works in one field may notwork well in another, or what works for one producer maynot work for another. Considerable research has been done,especially in the High Plains, evaluating different methods

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for conserving and delivering water to crops. Low EnergyPrecision Application (LEPA) systems have been developedand are widely used.

Many growers use different variations of this system. Somefarmers drag socks or tubes in circular rows, others dragtubes on straight rows, still others use the bubble-mode fordelivering irrigation water. Research has shown that opti-mum peanut yields can be attained with LEPA on circularrows using drag socks in alternate furrows, at a water appli-cation rate equal to 75 percent of the recorded cotton evap-otranspiration rate.

Peanuts require about 1.5 to 2.0 inches of water per week,especially between early July and mid-August. This timeperiod coincides with peak bloom, peg and pod set. Oncefull canopy development has been achieved, water use issimilar to pan evaporation, indicating that water use rangesfrom 0.25 to 0.40 inch per day (depending upon weatherconditions).

Water use by peanuts will peak in late July through August.If 0.75 inch of water is applied twice weekly, this will notsupply as much water as the plants actually use.Consequently, stored water in the 2- to 3-foot depths will beused by the plants. During August, transpiration and evapo-ration will often range between 0.25 and 0.35 inch per day,depending on weather conditions. This amounts to 1.75 to2.45 inches of water per week. As stated previously, two0.75 inch applications each week total 1.5 inches, whichemphasizes the need for entering the season with a full pro-file of water when possible.

Uniform moisture that can be maintained with two irriga-tion applications per week helps to ensure adequate soilmoisture and high relative humidity in the canopy. Thepeanut plant flowers in response to elevated humidity andpod set is enhanced by elevated humidity and moist surfacesoils. Consequently, yield is positively affected by anextended period of high humidity during the critical 45 to90 days after emergence. Holding humidity high during this45-day period in the growth cycle not only increases yield,but promotes a uniform early pod set, resulting in early

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maturity and harvest. Also, it creates less exposure to pod-rotting diseases. The pegging zone should be kept moisteven though adequate moisture may be available deeper inthe profile.

After kernels begin to fill (late August to early September)the amount of irrigation water can be slightly reduced.However, any reductions in irrigation will be based on cropmaturity and rainfall. Changing from a twice-a-week to aonce-a-week irrigation schedule helps stop blooming. Lowerrelative humidity in the canopy moves the crop into a mat-uration phase and reduces susceptibility to pod rot organ-isms. A good rule of thumb to help gauge the last 30 to 40days of the season is to not the let the crop show visiblesigns of stress in the morning hours. During the maturationperiod, the plants will be mobilizing nutrients and foodreserves to the developing kernels. In addition, plant wateruse during maturation is moderate compared to the criticalbloom, peg and pod development periods. Try to avoid largefluctuations in pod zone moisture to prevent hull splitting,which leads to increased loose shelled kernels. Looseshelled kernels correlate highly with aflatoxin problems.

Weed Management

Weeds in peanuts can be managed by using cultural,mechanical, physical and chemical means. A combinationapproach provides the most successful results. Considera-tions for cultural and mechanical weed control include:

■ Remove spotty infestations by hand hoeing or spot spray-ing to prevent spreading weed seed, rhizomes, tubers orroots. This is particularly important for perennial weedspecies.

■ Use high quality, weed-free seed. Bar-ready seed is avail-able from shellers and has had nutsedge tubers removed.

■ Clean all tillage and harvesting equipment before movingto the next field, or from weedy to clean areas within afield.

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■ Use cultivation or burn down herbicides to remove ini-tial weed flushes prior to planting to ensure a weed-freeseedbed.

■ Keep turn rows, fence rows, bar ditches and other areasadjacent to fields clean.

■ Practice crop rotation.

Weed management is critical to peanut production fromboth yield and quality perspectives. Weeds reduce growerprofits in several ways. Weed/crop competition for sunlight,water and nutrients can significantly lower yields. Weedsalso disrupt digging and harvesting operations and causepods to be stripped from vines, making them unhar-vestable. In addition, weed problems can lower gradesbecause plant fragments and fruits are classified as foreignmaterial contamination.

Research indicates that if peanuts are kept weed-free for 4to 6 weeks, then yield reductions from weeds will be mini-mized. Therefore, it is most important to use a preplantincorporated dinitroaniline herbicide (Treflan [Trifluralin],Prowl, Sonalan) for full-season weed management. Careshould be taken to ensure proper application rate of thedinitroaniline herbicides. Excessive rates can lead to peanutinjury and reduced yields. Do not use cotton rates.

CultivationBecause of their growth habit, peanuts are not well-suitedfor conventional cultivation methods. Movement of soilonto peanuts can cause several problems. The lower nodesof the lowest lateral branches will be covered with soil,which inhibits normal flower, peg and pod set and reducesproduction. Soil thrown to the crown and lateral portions ofthe peanut plant creates favorable conditions for southernblight and other diseases. Plow sweeps should be operatedflat and shallow to remove weeds without dirting the plantsand pruning lateral roots.

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Management of Selected Weed SpeciesNutsedge Complex—Yellow and purple nutsedge can oftenbe major problems in peanuts. Both nutsedge species willbe similar in appearance, however, control measures maybe quite different. Therefore, proper identification is criticalto successful control. The easiest way to identify yellowand purple nutsedge is late in the season when the seedhead has developed. The seed head of yellow nutsedge willhave a yellow coloration, while those of purple nutsedgewill have a purple color—hence the names. There are somecharacteristics that can be used to identify the two speciesearlier in the season, however, experience with both speciesis often needed to detect these subtle differences. First, thetubers of purple nutsedge will be connected in chains,while the tubers of yellow nutsedge are not connected. Theleaf tips of yellow nutsedge will come to a sharp point andoften start to die back. Leaf tips of purple nutsedge will bemore rounded. Purple nutsedge will often have darkergreen appearance than yellow nutsedge. Finally, tubers ofyellow nutsedge will have a sweet smell, while tubers ofpurple nutsedge will smell bitter.

Both species are perennial weeds that are mainly intro-duced into new fields through tubers. Plant peanut seedthat is free of weed seed and tubers. Bar-ready seed con-tains few if any nutsedge tubers. Also, equipment should bethoroughly cleaned of any nutsedge plants when movingfrom field to field.

Fortunately, with the introduction of new herbicides, thereare control options available for both yellow and purplenutsedge. Good control of yellow nutsedge can be obtainedwith preplant incorporated applications of Dual Magnum orFrontier. Preemergence applications of Dual Magnum orFrontier will provide some control of yellow nutsedge, butare not as effective as preplant incorporated treatments.Most growers in Texas prefer to make postemergence appli-cations of these materials after the peanuts have emerged.This method reduces any potential injury from the herbi-cides; however, timely rainfall or irrigation shortly afterapplication is needed to activate the herbicide. Postemer-

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gence applications of Basagran or Tough have providedgood control of yellow nutsedge; however, repeat applica-tions probably will be needed for adequate control. DualMagnum, Frontier, Basagran and Tough do not controlpurple nutsedge.

Pursuit applied preplant incorporated, preemergence orpostemergence (only postemergence applications arelabeled for west Texas) and Strongarm applied preemer-gence will provide fair to good control of yellow nutsedgeand excellent control of purple nutsedge. Cadre appliedpostemergence will provide excellent control of both yellowand purple nutsedge. Adequate and timely irrigation willimprove control with these products.

Eclipta—Eclipta can be a problem in north, central andsouth Texas regions, especially in low lying and wet areasof fields. Also, fields irrigated from holding ponds andreservoirs generally have more eclipta problems. It is recog-nizable by its long, narrow leaves attached directly to thestem, and very small white flowers. Recognizing eclipta inthe field early is key to its management. Unfortunately,once eclipta gets 4 to 6 inches tall it becomes very difficultto control. Eclipta often germinates late in the season, afterresidual herbicides have dissipated and after postemergencetreatments have been made. Consequently, it can get estab-lished late in the season. Dual Magnum or Frontier appliedpreplant incorporated or preemergence can provide earlyseason eclipta control. If these materials are applied poste-mergence, they will not control eclipta that has alreadyemerged, but will provide residual control of eclipta thathas not yet emerged. Strongarm applied preemergence pro-vides excellent control of eclipta.

Postemergence options for eclipta include Basagran, Blazer,Storm and Tough. Best results are obtained when applied toeclipta that is less than 2 inches tall. Cadre provides somecontrol, but the application must be made to very smalleclipta.

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Pigweed—The foundation for good pigweed control isusing a dinitroaniline herbicide. When used at the appropri-ate rate and properly incorporated, Treflan, Prowl andSonalan provide good to excellent pigweed control. Becauseincorporation methods vary across the state, use a methodthat provides a uniform distribution of the herbicide intothe top 1 to 2 inches of the soil. If soil conditions are dryand large clods are present before and after application,herbicide performance will be reduced. Although the dou-ble-pass method is recommended (the second incorporationshould be made at an angle to the first) a single-pass can beeffective when the soil is of good tilth and moisture.Strongarm, Dual Magnum and Frontier have good activityon pigweed, but are usually not used as stand-alone treat-ments. Therefore, these materials are usually considered asimproving the effectiveness of the dinitroaniline herbicide.

Pigweed escapes can be effectively controlled if the weedsare treated when small. Pursuit, Cadre, Blazer, Storm, and2,4-DB have good activity on small pigweeds.

Morningglory—Dinitroaniline herbicides do not provideeffective morningglory control, nor do preemergence mate-rials such as Dual Magnum and Frontier. Strongarm appliedpreemergence provides good control of annual morning-glory species.

Blazer, Pursuit and Storm provide fair to good control ofmorningglory, but weed size is very important—the smallerthe better. Cadre applied early-postemergence to smallmorningglories (3 inches tall) provides good to excellentcontrol, and 2,4-DB provides good to excellent control ofmorningglories of larger size.

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Table 8. Preplant Soil Incorporated ProductsProduct and

Weeds Controlled Rate/Acre RemarksAnnual grasses and Prowl 3.3 EC Incorporate within 7 dayssmall seeded broadleaf 1.2 to 2.4 pts after application.weeds such as pigweed, barnyardgrass, goose- Sonalan HFP Incorporate within 48grass, Texas panicum, 1.5 to 2 pts. on hours after application.seedling johnsongrass, coarse soilsfall panicum, broadleaf 2.0 to 2.5 pts.signalgrass on medium soils

Treflan HFP Incorporate immediately(Trifluralin) after application.1.0 pt.

Yellow nutsedge, barn- Dual Magnum Does not adequately con-yardgrass, crabgrass, 0.8 to 1.33 pts. trol Texas panicum. Injuryfall panicum, broadleaf may occur following usesignalgrass, pigweed, if it is incorporated toocarpetweed deeply, or very high rain-

fall conditions move the herbicide into the germi-nation zone.

Frontier 6.0 Does not adequately con-20 to 32 oz. trol Texas panicum.

Yellow and purple nut- Pursuit DG Shallow incorporationsedge, devil’s-claw, 1.44 oz. (1 to 2 inches deep)pigweed, teaweed, preferable. May be tank-spurge, sunflower, mixed with Prowl,annual morningglory, Sonalan, Treflan andseedling johnsongrass Dual Magnum. Not

labeled for preplant incorporated or pre-emergence applications in West Texas, wait until late-cracking when most of the peanuts have emerged.

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Table 8. Preplant Soil Incorporated Products (continued)Product and

Weeds Controlled Rate/Acre RemarksYellow and purple nut- Do not apply more than sedge, devils claw, 1.44 oz. Pursuit 70 DG pigweed, teaweed, per acre, per season. spurge, sunflower, 18-month rotation restric-annual morningglory, tion for cotton and seedling johnsongrass sorghum.(continued) .

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Table 9. Preemergence Products

Product andWeeds Controlled Rate/Acre Remarks

Yellow and purple nut- Pursuit DG Premergence applicationssedge, devils claw, 1.44 oz. depend on rainfall orpigweed, teaweed, irrigation for activation.spurge, sunflower, Preemergence applica-annual morningglory, tions are less consistentseedling johnsongrass than preplant incorporated

treatments. Not labeled for preplant incorporated or preemergence applica-tions in West Texas, wait until late-cracking when most of the peanuts have emerged. Do not apply more than 1.44 oz. Pursuit 70 DG per acre per sea-son. 18-month rotation restriction for cotton and sorghum.

Yellow nutsedge, barn- Dual Magnum Either rainfall or irrigationyardgrass, crabgrass, 0.8 to 1.33 pts. is needed for effectivefall panicum, broadleaf results from preemer-signalgrass, pigweed, gence applications. A pre-carpetweed emergence application is

less effective than a pre-plant incorporated treat-ment for yellow nutsedge control. Does not ade-quately control Texas panicum.

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Table 9. Preemergence Products (continued)

Product andWeeds Controlled Rate/Acre Remarks

Yellow nutsedge, barn- Frontier 6.0 Either rainfall or irrigation yardgrass, crabgrass, Outlook is needed for effective fall panicum, broadleaf 20 to 32 oz. results from preemer-signalgrass, pigweed, gence applications. Acarpetweed preemergence application (continued) is less effective than a

preplant incorporated treatment for yellow nutsedge control. Does not adequately control Texas panicum.

Cocklebur, lambsquarter, Strongarm 84WG Apply at rate of 0.45 oz.common ragweed, 0.45 oz. as a preemergencedevil’s-claw, prairie application from no lesssunflower, common than 5 days after plant-sunflower, golden crown- ing through at-crackingbeard, morningglory, stage. Do not applypigweed, teaweed, Strongarm to soils withspurred anoda, tropic pH of 7.2 or greater.croton, velvetleaf, eclipta, copperleaf, yellow and purple nutsedge, smartweed

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Table 10. Postemergence Products

Product andWeeds Controlled Rate/Acre Remarks

Yellow and purple nut- Pursuit DG Apply to actively growingsedge, devils claw, 1.44 oz weeds less than 3 inchespigweed, cocklebur, tall to be most effective.teaweed, spurge, annual Always use a nonionicmorningglory, seedling surfactant (1 qt./100 gal-johnsongrass lons of spray solution)

or crop oil concentrate (1 qt./acre). Addition of nitrogen fertilizer (28 % N, 32 % N, ammonium sul-fate) may improve control. May be tankmixed with 2,4-DB for broader spec-trum weed control. Will provide residual control when activated by rainfall, irrigation or shallow cultiva-tion. 18-month rotation restriction for cotton and sorghum.

Yellow and purple nut- Cadre DG Apply to actively growingsedge, devils claw, 1.44 oz. weeds less than 4 inchespigweed, cocklebur, tall to be most effective.teaweed, spurge, annual Always use a nonionicmorningglory, seedling surfactant (1 qt./100 gal-johnsongrass, prairie lons of spray solution) orsunflower, golden crown- crop oil concentrate (1beard, yellow top, pie qt./acre). Addition of nitro-melon, shining tickseed, gen fertilizer (28 % N, 32Russian thistle, sicklepod % N, ammonium sulfate)

may improve control. Will provide residual control when activated by rainfall, irrigation or shallow cultiva-tion. Peanuts should be emerged before making

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Table 10. Postemergence Products (continued)

Product andWeeds Controlled Rate/Acre Remarks

Yellow and purple nut- application. Cadre may sedge, devils claw, cause some peanut yellow-pigweed, cocklebur, ing and/or reduced vine teaweed, spurge, annual growth, but yields are morningglory, seedling unaffected. 18-month johnsongrass, prairie rotation restriction for sunflower, golden crown- cotton and sorghum.beard, yellow top, pie melon, shining tickseed,Russian thistle, sicklepod(continued)

Buffalobur, cocklebur, Blazer Treat when broadleafcommon ragweed, Ultra Blazer weeds are small (2 to 6groundcherry, lambs- 1.0 to 1.5 pts. leaves) and actively grow-quarter, purslane, ing for best results. Consultmorningglory, pigweed, label for specific weedtropic croton, prostrate problems. Copperleafspurge, carpetweed, should be less than 4 inch-black nightshade, spiny es tall and eclipta should cucumber, smellmelon, be less than 2 inches tall.Texas gourd, copperleaf, Blazer is a contact eclipta, golden herbicide; therefore, goodcrownbeard coverage is essential.

Always use nonionic sur-factant (1 qt./100 gallons spray solution) or crop oil concentrate (1 to 2 pts./ acre). Do not apply within 75 days of harvest. Blazerwill cause spotting andbronzing of contacted peanut leaves.

40

Table 10. Postemergence Products (continued)

Product andWeeds Controlled Rate/Acre Remarks

Balloonvine, coffee Basagran Treat when broadleafsenna, common ragweed, 1.0 to 2.0 pts. weeds are small anddayflower, devil’s-claw, actively growing. ConsultPennsylvania smartweed, label for specific weedteaweed, spurred anoda, problems. For yellowtropic croton, velvetleaf, nutsedge, use 2.0 pts./acrewild sunflower, cocklebur, and apply when nutsedgeyellow nutsedge, eclipta is 6 to 8 inches tall. Always

use 1 to 2 pts./acre crop oil concentrate. Peanuts are tolerant at any growth stage.

See Blazer and Storm (premix of Treat when broadleaf Basagran weed lists. Blazer and weeds are small and

Basagran) actively growing. Consult 1.5 pts. label for specific weed

problems. Always use non-ionic surfactant (1 qt./100 gallons spray solution) or crop oil concentrate (1 to 2 pts./acre).

Cocklebur, eclipta, Tough 3.75 EC Treat when broadleafcopperleaf, ragweed, 2.0 to 3.0 pts. weeds are small andvelvetleaf actively growing. Tough

can be tankmixed with 2,4-DB for improved weed control. Tough does not provide adequate control of palmer pigweed. Eclipta should be less than 2 inch-es tall and copperleaf less than 4 inches tall.

41

Table 10. Postemergence Products (continued)

Product andWeeds Controlled Rate/Acre Remarks

Morningglory, cocklebur, 2,4-DB 1.75 Treat when broadleaf pigweed, velvetleaf, pie 0.9 to 1.8 pts. weeds are small and active-melon, silverleaf night- ly growing. Use the low rateshade 2,4-DB 200 on morningglory and cock-

0.8 to 1.6 pts lebur up to 12 inches in size. For silverleaf night-shade suppression use higher rate. Crop oil con-centrate increases effective-ness, especially on hard-to-control weeds; however, this treatment causes the peanut canopy to lay down for a few days. Can be tank mixed with other com-pounds for enhanced weed control. Do not make more than two applications during the season. Do not allow herbicide to drift to suscep-tible crops such as cotton. Do not apply within 30 days before harvest.

Yellow nutsedge, goose- Dual Magnum Use as a supplement tograss, barnyardgrass, 0.8 to 1.33 pts. preplant incorporated treat-crabgrass, fall panicum, ments. Must be activated broadleaf signalgrass, by rainfall or irrigation.pigweed Dual Magnum will not con-

trol emerged grasses and broadleaf weeds; however, it will effectively control emerged yellow nutsedge.

42

Table 10. Postemergence Products (continued)

Product andWeeds Controlled Rate/Acre Remarks

Yellow nutsedge, goose- Frontier 6.0 Use as a supplement tograss, barnyardgrass, Outlook preplant incorporated treat-crabgrass, fall panicum, 20 to 32 oz. ments. Must be activated broadleaf signalgrass, by rainfall or irrigation. Dual pigweed Magnum will not control (continued) emerged grasses and

broadleaf weeds; however, will effectively control emerged yellow nutsedge.

Annual grasses including Select 2EC Treat when grasses arebarnyardgrass, broadleaf 8.0 to 16 oz. actively growing. See labelsignalgrass, fall panicum, for height restrictions. goosegrass, seedling Poast Plus Use crop oil concentratejohnsongrass, Texas 1.5 to 2.25 pts. at 1qt./acre rate. Do notpanicum apply to peanuts within 40

days of harvest. Avoid contact with corn, sorghum and small grains.

Bermudagrass Select 2EC Apply to actively growing8 to 16 oz. bermudagrass before run-

ners (stolons) exceed 6 inches. A second application of 12 oz. is usually neces-sary for good control. The second application should be made when regrowth is 4 inches in length. Use crop oil concentrate at 1qt./acre rate. Avoid contact with corn, sorghum and small grains.

43

Table 10. Postemergence Products (continued)

Product andWeeds Controlled Rate/Acre Remarks

Bermudagrass Poast Plus Apply to actively growing(continued) 2.25 pts. bermudagrass before run-

ners (stolons) exceed 6 inch-es. A second application of 1.5 pts. is usually necessary for good control. The second application should be made when regrowth is 4 inches in length. Use crop oil concen-trate at 1qt./acre rate. Avoid contact with corn, sorghum and small grains.

Rhizome johnsongrass Select 2EC Apply to actively growing8 to 16 oz. johnsongrass that is 15 to

25 inches tall. A second application of 12 oz. may be needed when new plants or regrowth are 6 to 12 inches tall. Use crop oil concentrate at 1qt./acre rate. Avoid con-tact with corn, sorghum and small grains.

Poast Plus Apply to actively growing1.5 to 2.25 pts. johnsongrass that is 15 to 25

inches tall. A second applica-tion of 1.5 pts. may be need-ed when regrowth or new plants are 6 to 12 inches tall. Use crop oil concentrate at 1qt./acre rate. Avoid contact with corn, sorghum and small grains.

44

Table 11. Products, Formulations and Common Names of Herbicides

Product Formulation Common name

Basagran® 4 lbs./gallon bentazon

Ultra Blazer® 2 lbs./gallon acifluorfen

2,4-DB® 1.75 lbs./gallon 2,4-DB2.0 lbs./gallon

Cadre DG® one soluble packet contains imazapic0.125 lbs. active ingredient

Dual Magnum® 7.62 lbs./gallon s-metolachlor

Frontier 6.0® 6 lbs./gallon dimethenamid

Poast Plus® 1.0 lb./gallon sethoxydim

Prowl 3.3EC® 3.3 lbs./gallon pendimethalin

Pursuit DG® one soluble packet contains imazethapyr0.125 lb. active ingredient

Select 2EC® 2 lbs./gallon clethodim

Sonalan HFP® 3 lbs./gallon ethalfluralin

Storm® 2.67 lbs./gallon - bentazon bentazon-acifluorfen1.33 lbs./gallon - acifluorfen

Strongarm® 84 % active ingredient diclosulam

Tough 3.75 EC® 3.75 lbs./gallon pyridate

Treflan HFP® 4 lbs./gallon trifluralin

Weed/Herbicide Response RatingsWeed control research involves searching for methods andproducts to eliminate competition to the crop. Weed speciesin fields are constantly changing because of control of com-peting weeds; the introduction of new weeds in an area;changing cropping patterns, and herbicide usage rotationsand the introduction of new herbicides.

Weed control with herbicides can also be frustrating.Changes in soil texture, slope of fields, the time andamount of rainfall or irrigation, soil or air temperature,amount and type of surfactant, rate of herbicide, time of

45

application, size of weeds and crop condition at time of her-bicide application, are just a few of the variables that alterthe results of a herbicide application. The following infor-mation is the result of years of intensive research in Texas.

The ratings of each of the herbicides are a summary of testplots across Texas. Excellent (E) control is classified asgreater than 90 percent control, Good (G) is from 80 to 90percent, Fair (F) is 70 to 80 percent and Poor (P) is less than70 percent control; I is Inconsistent. Before applying anyproduct read and follow the label directions.

46

Tabl

e 12

. Wee

d/H

erbi

cide

Res

pons

e R

atin

gsPr

epla

ntTe

xas

Yello

wPu

rple

Bar

nyar

d-Si

gnal

-C

oppe

r-

Inco

rpor

ated

pani

cum

Nut

sedg

eN

utse

dge

gras

sC

rabg

rass

gras

sEc

lipta

Pigw

eed

Sunf

low

erYe

llow

top

leaf

Mor

ning

glor

ies

Prow

lE

PP

EE

EP

G/E

FG

FP

Tref

lan

EP

PE

EE

PG

/EF

GF

P

Sona

lan

EP

PE

EE

PG

/EF

GF

P

Purs

uit

PF/

GF/

GG

/EF

FP

EE

GF/

GF

Dua

lP

F/G

PF/

GG

FF/

GG

GG

P/F

F

Fron

tier

PG

PF/

GG

FF/

GG

GG

P/F

F

Pre-

Texa

sYe

llow

Purp

leB

arny

ard-

Sign

al-

Cop

per-

em

erge

nce

pani

cum

Nut

sedg

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gras

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rabg

rass

gras

sEc

lipta

Pigw

eed

Sunf

low

erYe

llow

top

leaf

Mor

ning

glor

ies

Dua

lP

F/G

PF/

GF/

GP

F/G

GF

FF

P

Fron

tier

PF

PF/

GF/

GP

F/G

GF

FF

P

Purs

uit

PP/

FF/

GP

PP

PG

/EF

PP

F

Stro

ngar

mP

F/G

F/G

PP

PE

EE

EF/

GF/

G

47

Tabl

e 12

. Wee

d/H

erbi

cide

Res

pons

e R

atin

gs (c

ontin

ued)

Post

Texa

sYe

llow

Purp

leB

arny

ard-

Cra

b-Si

gnal

-C

oppe

r- S

icke

l-M

orni

ng-

Ber

mud

a-Jo

hnso

n-em

erge

nce

pani

cum

Nut

sedg

eN

utse

dge

gras

sgr

ass

gras

sEc

lipta

Pigw

eed

Sunf

low

erYe

llow

top

leaf

pod

glor

ies

gras

sgr

ass

Basa

gran

PF/

GP

PP

PE

PP

PP

PP

PP

Blaz

erP

PP

PP

PE

EG

GG

PF/

GP

P

2,4-

DB

PP

PP

PP

PF

GG

PG

GP

P

Cad

reG

G/E

G/E

EE

EF

GE

EF

EG

/EP

F

Dua

lP

F/G

PP

PP

PP

PP

PP

PP

Fron

tier

PF

PP

PP

PP

PP

PP

PP

P

Poas

t Plu

sG

/EP

PE

EE

PP

PP

PP

PF

F

Sele

ctE

PP

EE

EP

PP

PP

PP

F/G

G/E

Purs

uit

PG

EP

PP

PE

GG

PP

GP

P

Stor

mP

FP

PP

PG

FF

FF

PG

PP

Toug

hP

GP

PP

PE

PP

PG

FP

PP

48

Disease and NematodeManagement

All peanut producers experience crop loss from one ormore diseases annually. Refer to the Peanut Disease Atlas(B-1201), available from your county Extension agent forhelp with disease diagnosis. Diseases can be controlled byusing appropriate preventative practices. Control sugges-tions made in this publication have been well documentedin field tests over a period of years and have been shown toproduce economic benefit when appropriately applied.Potential economic benefit depends on each grower’s abilityto adapt controls to his production system and prevailingenvironmental conditions.

Seed Rot and Seedling Disease ControlPlant high quality seed treated with a seed protectant fungi-cide (Table 13). Seedling disease is less severe when soiltemperatures average 70 degrees F or more at a 2-inchdepth at 7 a.m. for 3 consecutive days.

Foliar Disease Control

Early Leaf Spot and Late Leaf SpotCombine chemical (Table 14) and cultural practices formore consistent control. Rotation with other crops reducesoverwintering populations of leaf spot fungi in the soil andmakes chemical disease control more effective and prof-itable. Shorter application intervals and maximum rates ofchemicals become necessary when disease pressure isgreatest and weather conditions favor additional infection.Early detection of leaf spot requires close observation. Beaware that different fungicides perform in different waysunder varying weather conditions. Always read and followlabel directions carefully.

Chemical control methods for irrigated peanuts:

Spanish and Valencia types—Begin fungicide applications35 to 40 days after planting and continue at recommended

intervals until 20 to 21 days before harvest, depending onthe fungicide used, weather conditions and disease develop-ment.

Runner and Virginia types—Begin applications 50 to 55days after planting. Follow the Spanish recommendationsabove if late leaf spot occurs during the early stage of plantdevelopment.

Chemical control methods for dryland peanuts:

Follow the recommendations for irrigated peanuts if rainfallis sufficient for continuous plant growth and disease devel-opment. In years of low rainfall and low humidity, beginfungicide applications at first evidence of either leaf spotdisease or when rains or dew favor disease development.Continue applications at suggested intervals through peri-ods suitable for leaf spot development. Dew formation ismost consistent in the fall, beginning in September, butmay occur anytime.

RustPeanut rust usually occurs sporadically in a geographicallylimited area except in South Texas where it occurs annually.The fungus has not been observed to overwinter in Texas,and each year spores must be blown in from the Caribbeanarea. Rust is typically found in South Texas peanuts in mid-July. Once established, rust can develop rapidly duringhumid wet weather. Late planted peanuts in South Texasare most vulnerable because rust spores produced in near-by early planted fields are carried on prevailing winds toother fields. Apply fungicides effective against rust (Table14) at shortest intervals at the first sign of rust in fields orin nearby fields.

Web BlotchSpanish and Valencia market type peanuts are more suscep-tible than runner and Virginia types to web blotch.However, runner types in West Texas can experience severedamage from this disease. Several foliar fungicides areeffective (Table 14).

49

Application MethodsFoliar fungicides may be applied with ground or air equip-ment in spray formulations. Use any method that evenlydeposits the protective fungicide on the entire leaf surface.Use three hollow-cone nozzles per row spaced for optimumcoverage. Make the first three applications in a band withground equipment to control foliar diseases and reduceearly season cost. If a three-nozzle arrangement is used (onenozzle at the top and two on the sides), plug the side noz-zles for the first application and use only the top one. Usetwo nozzles on larger peanuts 10 to 14 days later by plug-ging the top one and using the two side nozzles. For thethird and subsequent applications, use all three nozzleseven though this may damage some vines. Ground sprayequipment should apply the suggested amount of fungicidein 10 to 25 gallons of water per acre, depending on vinesize. Careful use of ground equipment has little or noadverse effect on yield. When applying fungicides by air,use at least 5 gallons of water per acre. Demonstrationsunder field conditions show that foliar fungicides appliedthrough sprinkler irrigation systems give control equal tothose applied by air and ground equipment. Continuousagitation of fungicide-water combinations to prevent fungi-cide settling is required when the center pivot system cir-cles. This is not a problem with side-roll injection systems.

Aerial application of foliar fungicides provides good controlwhen equipment is properly adjusted and operated.Adequate flagging, marking or positioning with global posi-tioning systems ensures even distribution and avoids swathwidths that are too wide. Stop application if temperaturesare above 90 degrees F and relative humidity is below 45percent to avoid spray droplets drying before hitting targetplants. A visible blanket of spray mixture will appearbehind the aircraft when the 5-gallon per acre rate is used.

Control of Pod, Peg and Stem FungalDiseases

Southern BlightCultural methods for control of southern blight include:

50

51

1. Rotate crops to avoid peanuts following peanuts.

2. If peanuts follow peanuts in successive years, bury cropresidue with a moldboard plow deep enough to avoidbringing residue back up during land preparation andcultivation. There may be no advantage in buryingresidue from nonpeanut crops.

3. Plant on a raised bed. Plant dryland peanuts on a slightlyraised bed and irrigated peanuts on a bed at least 4 inch-es high.

4. Avoid high seeding rates. Early development of a densecanopy retains humidity that favors the southern blightfungus.

5. Do not throw soil onto peanut plants during cultivation.

6. Control foliar diseases with fungicides to prevent leafshed. Fallen leaves are a food source for the southernblight fungus.

7. Dig when mature.

Chemical control of southern blight is possible with Folicur,Abound, Tilt, Montero or PCNB when used correctly (Table15). Multiple applications of Folicur, Tilt, Montero orAbound as preventative treatments in problem fields aresuggested rather than single applications or rescue treat-ments after southern blight damage has occurred. Considerthese characteristics when selecting a chemical. Fungicidesmay be labeled for application through sprinkler irrigationsystems in Texas and show acceptable levels of controlwhen used in this manner. Producers must be aware ofstrict regulations that exist regarding “chemigation” as itrelates to the potential for water contamination.

Positive disease identification is necessary to get economicreturns from chemicals. For example, all five previouslymentioned products are effective against the southernblight fungus but only Abound helps control the Pythiumpod rot fungus (Table 15).

52

Sclerotinia BlightSclerotinia blight, caused by the fungus Sclerotinia minor,was observed for the first time in Texas peanuts in 1981.Additional outbreaks of the disease have been identified innumerous Texas counties. The disease is characterized inearly stages by small white tufts of cottonlike growth onthe stems near the ground line at leaf axils. The fungusspreads rapidly. Later stages of the disease show up assevere stem shredding, almost as if the stems had exploded,accompanied by the production of many small, black, irreg-ular-shaped sclerotia that are approximately the size, shapeand color of mouse droppings. The distinguishing fielddiagnostic symptom is rapid plant death, accompanied bystem shredding. At first glance, this disease may be con-fused with southern blight, caused by the fungus Sclerotiumrolfsii. This mistake can be devastating because chemicalsthat control southern blight have no effect on theSclerotinia fungus. Research from several states has shownthe Sclerotinia fungus can be seed-borne. The sclerotia mayalso be spread by diggers, combines or vehicles carryinginfested soil or crop residue. Research at Stephenville hasshown that sulfur (applied as a foliar fungicide) significant-ly increases the severity of Sclerotinia blight.

The only fully labeled product for Sclerotinia blight controlis Rovral (Table 15). Rovral applied by ground requireslarge volumes of water (40 to 60 gallons per acre) to obtainmaximum effectiveness. A multiyear rotation, in conjunc-tion with deep burial of crop residue, is also helpful.Sclerotinia blight is more severe on runner than Spanishvarieties, supposedly because of quicker, more completeground cover with the runner types. Tamspan 90 has signif-icantly more resistance to the fungus than other availableSpanish and runner varieties (Table 17). Keep soil moisturebelow field capacity for the final 45 days to allow soil tem-perature to increase and help control the organism. Plantearly where possible to avoid cool fall temperatures con-ducive to the disease.

Botrytis BlightBotrytis blight is caused by a species of the fungus Botrytis.It has only been a significant problem in far West Texas.Since symptoms so closely resemble Sclerotinia blight, a labdiagnosis is necessary. Benlate, labeled for web blotch con-trol in peanut, is effective against Botrytis blight.

Pythium and Rhizoctonia DiseasesDiseases caused by these two groups of fungi can occuralone but more often occur together. Pythium fungi causepod rot and root rot. Rhizoctonia fungi cause disease onpods, pegs, limbs, leaves and roots. Pod rots are difficult tocontrol and cultural practices should be adjusted beforeconsidering a fungicide (Table 15). Cultural recommenda-tions for southern blight control are helpful for Rhizoctoniaand Pythium pod rot control.

■ Avoid excessive irrigation.

■ Rotate with unrelated crops. If possible, summer fallowduring rotation. Use small grains as a winter cover crop.Turn this under deeply with other crop residue in thespring. Plant on a raised bed.

■ Improve drainage in low areas. Where salinity is a prob-lem, check for and break up hard pans to allow leachingof salts.

■ Apply gypsum (a calcium source) at pegging, especiallyin areas where sodium salts accumulate in the soil fromlow quality irrigation water. Large seeded Virginia typepeanuts require more calcium than runner and Spanishtypes.

■ Avoid excessive fertilizer.

Black MoldBlack mold caused by the fungus Aspergillus niger is a threatto peanut production throughout Texas. Low quality seeds,late plantings and drought and high soil temperature stressfor the first few weeks after planting have been associatedwith a high disease incidence. The fungus attacks thecrown or collar area near the soil line and may girdle and

53

54

kill the plant at any stage from seedling to harvest. Theblack, slightly fluffy fungus growth on lesions located justbelow the ground line is the best field diagnostic symptom.There are no adequate control recommendations. A goodrotation program, avoiding late planting and frequent, light,early season irrigations reduce losses.

Diplodia Collar RotRotating with nonrelated crops lowers populations of thisfungal organism in the soil. Diplodia has been less severe inplots where leaf spot was controlled with fungicides andwhere soil temperatures were reduced by irrigation andvine shading. Plant small grain rotation crops in problemfields and turn them under to achieve initial decompositionbefore planting.

Biological Control of Soil-borne FungiCertain fungal species in the genus Trichoderma feed onmycelium and sclerotia of Sclerotinia minor, Sclerotium rolfsiiand Rhizoctonia spp. All peanut fields in Texas tested todate have natural populations of Trichoderma. For severalyears, tests have been conducted in Texas using corn mealto stimulate Trichoderma development as a way to controlthe major soil-borne disease fungi. When yellow corn mealis applied to fields in the presence of moist surface soil,Trichoderma builds up very rapidly over 5 to 10 days. Theresulting high Trichoderma population can destroy vastamounts of Sclerotinia, Sclerotium and Rhizoctonia. Thisenhanced, natural biological control process is almost iden-tical to the processes that occur when crop rotation is prac-ticed. The level of control with corn meal is influenced byorganic matter source, soil moisture, temperature and pesti-cides used. Seasonal applications of certain fungicides mayinhibit Trichoderma. Testing will continue to determine therates and application methods that will give consistent, eco-nomical control.

Nematode ControlSeveral kinds of plant parasitic nematodes may cause dam-age but “root knot” caused by the peanut root knot nema-tode Meloidogyne arenaria is normally the most severe. Rootknot is easily diagnosed from galls on roots and usually alsoon pegs and pods. Other nematodes require soil and labora-tory analysis of plant samples for identification. The besttime to sample is at or near harvest. Send a soil sample rep-resentative of damaged areas, along with peanut pods ifavailable, to: Texas Plant Disease Diagnostic Laboratory,Texas Agricultural Extension Service, College Station, Texas77843. There is a $20 per sample fee. Nematode sampleforms are available at county Extension offices (Form D-827). Rotate with crops resistant to the nematodes damag-ing peanuts as a control program. Consider a nematicidewhen plant parasitic nematodes have previously limitedproduction.

Late maturing varieties have more potential for damagethan short-season Spanish market types.

Use caution when selecting a nematicide (Table 16) sincesoil moisture is extremely critical for optimum control.Telone II at rates of 6 to 12 gallons per acre works bestwhen placed 10 to 12 inches in the ground with a mold-board plow. Excessive soil moisture and cold temperatureslimit movement of the fumigant in the soil, reducing itseffectiveness and possibly causing plant stunting. Thisfumigant will cause fewer problems when applied at least10 to 14 days before planting. Granular contact nematicideswork best with good soil moisture conditions.

Aflatoxin (Segregation III)Aflatoxin is a chemical compound produced by the fungiAspergillus flavus and A. parasiticus. Aflatoxin may accumu-late before digging in drought stressed dryland peanuts.Reduce seeding rates in dryland fields to conserve soilmoisture. Some soils have a higher population of the fungusthan others. If peanuts from a field consistently have thiscondition, consider rotating with other crops. Irrigate if pos-sible because peanuts under drought stress are more sus-

55

ceptible to field infection by Aspergillus sp. Segregation IIIpeanuts are usually associated with preharvest drought con-ditions of kernel moisture below 25 percent and high soiltemperatures (80 to 100 degrees F). Pod injury from insectsor other agents favor infection by these fungi.

Aflatoxin may also accumulate during harvest and curing ifdrying conditions are less than ideal. Use inverting diggersto keep pods off the soil surface while curing within thewindrow. Adjust combines to prevent pod damage andtransport peanuts in vented trucks and trailers to preventheating. Force air through the truck or trailer and dry assoon as possible.

Aflatoxin may also accumulate during storage in regionswith high humidity or in facilities that leak during rains.

Varietal Characteristics Relativeto Disease DevelopmentPeanut varieties differ in their susceptibility to diseaseorganisms (Table 17). Tamspan 90 is less susceptible thanother varieties to Pythium pod rot. Although runner andSpanish peanuts are both affected by Pythium pod rot andsouthern blight, runner types suffer the most damage. Giverunner types extra consideration when chemical treatmentsare required.

Both Spanish and runner peanuts can be heavily damagedby root knot nematodes; however, the extra 30 days neededto mature the runner type magnifies their damage potential.Split applications of nematicide may be necessary for run-ner varieties. With the longer growing season needed forrunner peanuts and their partial resistance to early leafspot, late leaf spot often is the predominant foliage disease.Early leaf spot affects both types but is usually worse onSpanish varieties. Spanish varieties are also more suscepti-ble to web blotch. Large-seeded Virginia varieties appearmore prone to aflatoxin development than Spanish or run-ners under South Texas conditions. Where Sclerotinia blightis a problem, Spanish peanut varieties, particularlyTamspan 90, can often be grown without chemical control.Runner types are much more susceptible to the fungus.

56

Consider all these factors when planning a chemical controlprogram.

Virus Diseases

Spotted WiltYield loss from spotted wilt, caused by tomato spotted wiltvirus (TSWV), occurs in Southwest and Central Texas. Yieldlosses may exceed 50 percent in susceptible varieties.Tobacco thrips and western flower thrips are vectors (carri-ers).

Impatiens necrotic spot virus (INSV) was detected in peanutin Southwest Texas in 1998 and 1999 as single INSV infec-tions and double infections with TSWV. INSV is related toTSWV, but western flower thrips are more efficient vectorsof INSV than are tobacco thrips. The plant host lists aresimilar and symptoms are probably identical for TSWV andINSV.

TSWV and INSV overwintering sites are not completelyunderstood. Both viruses have large host ranges. Infestedtobacco thrips may overwinter in some soils. Westernflower thrips can be active throughout the year and mayspread one or both viruses during the winter among weedsand susceptible vegetable crops. Spinach and potato canharbor TSWV through the winter in South Texas. TSWV isnot known to be seed-borne in any crop or weed.

Typical early season spotted wilt symptoms include ringspotting of leaves and stunted plant growth; these symp-toms usually are not seen in late season spotted wilt. Olderplants that become infected with TSWV and apparentlywith INSV often simply turn yellow, wilt and quickly die.Plants also show signs of brown streaking within the vascu-lar system and deterioration of roots. TSWV can be detect-ed in the crown area of most plants in fields exhibitingthese symptoms in Southwest and Central Texas. INSV wasdetected sporadically in Southwest Texas in 1999.

Risk of spotted wilt is reduced by use of varieties withsome level of resistance. Resistant peanut varieties havefewer infected plants and those infected plants have milder

57

58

symptoms than more susceptible peanut varieties under thesame conditions. Spotted wilt epidemics are driven by twofactors. The first is how much virus is brought into the fieldby thrips. This varies widely from year to year (fall rainsusually increase risk for the following season) and fromfield to field. Peanuts planted in the proximity of TSWVhosts (spinach, potato, spring green bean) and early plantedpeanut fields may have increased risk. Very early and verylate planted fields usually have increased risk. Carefulplanting date and field selections may allow growers tomiss some thrips migrations in some years. The second andmore important factor is how fast the virus spreads frompeanut plant to peanut plant. Large thrips populations fromnearby cotton production may increase spread. The onlything known to slow down this type of spread is to increasethe level of variety resistance.

Anything that can be done to enhance overall plant healthmay prolong plant life and increase the chance of making acrop in spite of the virus. It is especially important to avoidover watering 4 to 6 weeks before digging infested fields.This does not control the virus, but helps keep infectedplants alive.

Efforts to develop superior resistant varieties for Texasgrowers (Table 17) continue. Variety options for partialTSWV resistance in 1999 include Tamrun 96, GeorgiaGreen, AT-108, ViruGard, Georgia Bold, Florida MDR-98,and Tamspan 90. Georgia Green may not be resistant toINSV.

TSWV-susceptible varieties such as Tamrun 88, Tamrun 98,AT-127 or Florunner increase the risk of spotted wilt wher-ever they are planted and, because the virus spreads, evenin nearby fields of more resistant peanuts.

Insecticides have not provided spotted wilt control. Consultan Extension entomologist for specific insect control infor-mation.

59

Atmospheric Scorch - OzoneNitrogen dioxide and hydrocarbons emitted from automo-biles, industrial combustion, oil refineries and other sourcesreact with sunlight to form ozone. Electrical storms produceozone that can be brought down from the upper atmos-phere by strong down drafts. The result on peanuts is ascorched appearance primarily on the upper leaf surface ofthe youngest leaves. Pepper spot caused by a species of thefungus Leptosphaerulina often invades these scorched leavesand enhances the damage. Regular use of a foliar fungicidehelps prevent these secondary infections in damaged tissue.

Salt and Boron DamageLow peanut yields and severe pod rots are potential prob-lems in soils with a high sodium adsorption ratio (SAR).The foliar symptoms that develop after irrigation withsaline irrigation water vary from a brown marginal leafletburn to death of the leaf. Pod rot often increases when sodi-um and potassium cations accumulate in the fruiting zone.Sodium and potassium apparently compete for position onsoil particles with calcium, a nutrient absorbed in largequantities by the developing pods. Calcium deficiency canbe associated with increased susceptibility to pod rot fungi.Supplements of gypsum (land plaster) can decrease pod rotunder high SAR conditions. Water infiltration into soil isdecreased in soils with high SAR. Furrow diking can reducerainfall and irrigation runoff and increase flushing of sodi-um from soil.

Boron toxicity is a problem in some soils in West Texas,decreasing plant growth and yields. The most commonsymptom is a yield decrease with little detectable foliagereduction.

Soil and irrigation water should be tested at least annuallyin areas at risk for high SAR or boron. Test results shouldbe considered when selecting fields for planting.

60

Tabl

e 13

. Pea

nut S

eed

Trea

tmen

t Fun

gici

des1

Seed

dec

ay a

nd d

ampi

ng o

ffFu

ngic

ide

Form

ulat

ion

Rhi

zoct

onia

Fusa

rium

Asp

ergi

llus

Pyth

ium

Rhi

zopu

sSc

lero

tinia

2

Baci

llus

subt

ilisG

BO3

Kodi

ak C

once

ntra

teBi

olog

ical

3✔

✔✔

capt

anC

apta

n 30

-DD

, 400

✔✔

✔✔

✔

capt

an +

PC

NB

+ ca

rbox

inVi

tava

x PC

✔✔

✔

fludi

oxon

ilM

axim

4FS

✔✔

✔✔

EBD

C (m

anco

zeb,

m

aneb

)nu

mer

ous

✔✔

✔✔

✔

met

alax

ylAl

legi

ance

-FL

✔

mef

enox

amAp

ron

XLLS

✔

PCN

BR

TU-P

CN

B✔

✔

PCN

B +

met

alax

yl +

Ba

cillu

s su

btilis

GBO

3Sy

stem

3✔

✔

thio

phan

ate-

met

hyl

Tops

90

✔✔

thira

mTh

iram

50W

P, 4

2-S

✔✔

✔✔

✔

1 Mos

t com

mon

ly u

sed

prod

ucts

are

Vita

vax

PC +

Top

sin,

Thi

ram

, PC

NB,

and

Vita

vax

PC a

lone

. See

d su

pplie

rs u

sual

ly d

eter

min

e se

ed tr

eatm

ent f

ungi

cide

.2 S

eed-

born

e Sc

lero

tinia

onl

y, n

ot s

oil-b

orne

inoc

ulum

.3 A

lso

for i

mpr

ovem

ent o

f nod

ulat

ion.

61

Tabl

e 14

. Pea

nut F

olia

r Fun

gici

des

Labe

led

for U

se in

Tex

asEa

rlyor

late

Web

Inte

rval

Hay

for

PHI1

Fung

icid

eFo

rmul

atio

nle

af s

pots

Rus

tbl

otch

(day

s)

liv

esto

ck(d

ays)

az

oxys

trobi

nAb

ound

F2

✔✔

✔10

-14

No

50

chlo

roth

alon

il; c

hlor

otha

loni

l +co

pper

, sul

fur3

, or p

ropi

cona

zole

num

erou

s, o

r tan

k m

ixtu

re✔

✔4

✔10

-14

No

14

copp

er, c

oppe

r + z

inc

num

erou

s✔

7-14

, 10-

14Ye

s0

fluto

lani

l + p

ropi

cona

zole

Mon

tero

2✔

21-3

0Ye

s540

man

coze

b, m

anco

zeb

+ co

pper

num

erou

s✔

✔3-

7, 7

-14

No

14

benz

imid

azol

e (b

enom

yl o

rBe

nlat

e, B

enla

te S

P, T

opsi

n M

thio

phan

ate-

met

hyl)

+W

SB2 ,

or T

opsi

n M

70W

2+

man

coze

b, e

tc.

man

coze

b, e

tc. t

ank

mix

ture

✔✔

7-14

No

14

prop

icon

azol

eTi

lt2✔

10-1

4Ye

s514

prop

icon

azol

e +

chlo

roth

alon

il Ti

lt Br

avo

✔✔

10-1

4N

o14

sulfu

r3nu

mer

ous

✔✔

7Ye

s0

tebu

cona

zole

Folic

ur 3

.6 F

2,6

✔✔

✔10

-14

No

14

triflo

xyst

robi

n +

prop

icon

azol

eSt

rate

go2

✔✔

✔10

-14

Yes5

141 P

reha

rves

t int

erva

l (m

inim

um d

ays

from

last

app

licat

ion

until

har

vest

)2 M

ay a

lso

be u

sed

to c

ontro

l cer

tain

soi

l-bor

ne fu

ngi.

3 Sul

fur m

ay in

crea

se a

Scl

erot

inia

blig

ht p

robl

em.

4 Rus

t not

men

tione

d on

Tilt

(as

tank

mix

ture

) or T

ilt/B

ravo

labe

ls.

5 Do

not f

eed

gree

n vi

nes

to li

vest

ock

or g

raze

live

stoc

k in

trea

ted

area

. 6 A

lso

labe

led

for p

eppe

r spo

t dis

ease

con

trol.

62

Tabl

e 15

. Pea

nut S

oil F

ungi

cide

s La

bele

d fo

r Use

in T

exas

Rhi

zoct

onia

Pyth

ium

seed

,So

uthe

rnSc

lero

tinia

seed

ling,

seed

ling,

pod

,B

lack

Rot

atio

nH

ay fo

rFu

ngic

ide

Form

ulat

ion

blig

ht1

blig

htpo

d ro

tpe

g, li

mb

rot

hull

rest

rictio

nliv

esto

ckPH

I2

azox

ystro

bin

Abou

nd F

3✔

✔✔

No

No

50ip

rodi

one

Rov

ral,

4F, W

G✔

Yes

No

10be

nom

yl +

Be

nlat

e, S

P+

man

coze

bm

anco

zeb,

etc

.3✔

No

No

14th

ioph

anat

e-m

ethy

l To

psin

M W

SB,

+ m

anco

zeb

70W

+ m

anco

zeb,

etc.

3✔

No

No

14m

efen

oxam

Rid

omil

Gol

d EC

, G

R, W

SP✔

Yes

Yes

0flu

tola

nil +

pr

opic

onaz

ole

Mon

tero

3✔

✔Ye

sYe

s440

PCN

Bnu

mer

ous

✔✔

Yes

No

45PC

NB

+ m

etal

axyl

Rid

omil

PC 1

1 G

✔✔

✔Ye

sN

o75

prop

icon

azol

eTi

lt3✔

Yes

No

21tri

floxy

stro

bin

+ pr

opic

onaz

ole

Stra

tego

3✔

Yes

Yes4

14te

buco

nazo

leFo

licur

3.6

F3

✔✔

Yes

No

141 G

ranu

lar i

nsec

ticid

e la

bels

for c

hlor

pyrif

os (L

orsb

an 1

5G) a

nd e

thop

rop

(Moc

ap 1

0G, M

ocap

10G

Loc

k ‘n

Loa

d) c

laim

enh

ance

s so

uthe

rn b

light

con

trol.

2 Pre

harv

est i

nter

val (

min

imum

day

s fro

m la

st a

pplic

atio

n un

til h

arve

st).

3 May

als

o be

use

d to

con

trol c

erta

in fo

liar p

atho

gens

. 4 D

o no

t fee

d gr

een

vine

s to

live

stoc

k or

gra

ze li

vest

ock

in tr

eate

d ar

ea.

63

Tabl

e 16

. Pea

nut N

emat

icid

es L

abel

ed fo

r Use

in T

exas

Tim

ing

Rot

atio

nH

ay fo

r

Form

ulat

ion

Prep

lant

Plan

ting

Pegg

ing

rest

rictio

nliv

esto

ckPH

I1

Fum

igan

t nem

atic

ides

chlo

ropi

crin

Chl

or-O

-Pic

✔N

oYe

s

dich

loro

prop

ene

Telo

ne II

✔2

No

Yes

di

chlo

ropr

open

e +

Telo

ne C

-35,

chlo

ropi

crin

C-1

7✔

No

Yes

m

etam

-sod

ium

num

erou

s✔

No

Yes

Con

tact

nem

atic

ides

aldi

carb

Tem

ik 1

5G,

Lock

‘n L

oad,

CP

✔✔

3,4

Yes

No

90et

hopr

opM

ocap

10G

,10G

Lock

‘n L

oad,

EC

✔✔

✔4,

5N

oYe

s

fena

mip

hos

Nem

acur

3, 1

5G✔

Yes

No

1 P

reha

rves

t int

erva

l (m

inim

um d

ays

from

last

app

licat

ion

until

har

vest

).2 D

emon

stra

tion

wor

k sh

ows

that

max

imum

rate

s an

d pl

acem

ent d

epth

s re

sult

in e

xcel

lent

con

trol o

f roo

t kno

t nem

atod

es.

3 Spl

it Te

mik

15G

app

licat

ion

for p

eggi

ng is

per

mitt

ed u

nder

Tex

as S

LN L

abel

78-

0013

. 4 T

emik

15G

at p

lant

+ M

ocap

10G

at p

eggi

ng is

som

etim

es s

uper

ior t

o Te

mik

15G

+ T

emik

15G

.5 O

nly

Moc

ap 1

0G fo

rmul

atio

ns a

re la

bele

d fo

r use

at p

eggi

ng.

64

Tabl

e 17

. Rea

ctio

ns o

f Tex

as P

eanu

t Var

ietie

s To

Pla

nt D

isea

ses1

Early

Late

leaf

leaf

Spot

ted

Pyth

ium

Web

Sout

hern

Scle

rotin

iaPe

pper

Bla

ckR

oot

Varie

tysp

otsp

otR

ust

wilt

pod

rot

blot

chbl

ight

blig

htsp

othu

llkn

otR

unne

r mar

ket t

ypes

Fl

orun

ner

SH

SS

SH

SR

HS

SS

SH

SAT

-120

SS

SR

S–

SS

HS

HS

HS

Tam

run

88S

HS

HS

HS

HS

SH

SS

SS

HS

Geo

rgia

Gre

enS

SS

RS

–S

SS

SH

STa

mru

n 96

SS

SR

S–

RS

SR

SC

oan

SH

SS

SH

SR

HS

SS

SR

Flav

or R

unne

r 458

SH

SS

SH

S

–H

SS

SS

HS

SunO

leic

97R

SH

SS

SH

S–

HS

SS

SH

SAT

-108

SH

SS

RS

–H

SS

SS

HS

Viru

Gar

dS

SS

HR

HS

–H

SS

HS

SH

SG

K-7

SH

SS

RH

S–

HS

SS

SH

SG

eorg

ia R

unne

rS

HS

SS

S–

HS

SS

SH

STa

mru

n 98

SS

SS

SS

SR

SS

HS

Flor

ida

MD

R-9

8S

RS

RS

–R

SS

SH

SG

eorg

ia B

old

SS

SR

S–

SS

SS

HS

65

Tabl

e 17

. Rea

ctio

ns o

f Tex

as P

eanu

t Var

ietie

s To

Pla

nt D

isea

ses1

(con

tinue

d)Ea

rlyLa

tele

afle

afSp

otte

dPy

thiu

mW

ebSo

uthe

rnSc

lero

tinia

Pepp

erB

lack

Roo

tVa

riety

spot

spot

Rus

tw

iltpo

d ro

tbl

otch

blig

htbl

ight

spot

hull

knot

Span

ish

mar

ket t

ypes

Tam

span

90

HS

HS

SR

RS

SR

S–

HS

Span

coH

SH

SS

SH

SS

SS

S–

HS

Pron

toH

SH

SS

SS

HS

SS

S–

HS

Virg

inia

mar

ket t

ypes

NC

-7S

SS

–S

SS

SS

SH

SVa

lenc

ia m

arke

t typ

es

Va

lenc

iaS

S–

–S

SS

SS

HS

HS

1 Rat

ings

are

: HS=

high

ly s

usce

ptib

le, S

=sus

cept

ible

, R=r

esis

tant

, HR

=hig

hly

resi

stan

t and

“—” u

nkno

wn

due

to in

suffi

cien

t tes

ting.

66

Insect Management

To achieve effective, economical insect control, insecticideapplications should be based on field inspections of pestpopulations. Use chemicals only if economically damagingpopulations of insects develop. Knowing when not to makean application is as important as knowing when to makeone. Beneficial insect parasites and predators should beprotected.

White GrubsWhite grub, the immature stage of the June beetle, recentlyhas caused considerable concern for peanut producers insouth Texas counties. White grubs feed on the secondary orfeeder roots of the plant, leaving the tap root intact. Plantsappear to die of drought stress because there are no hairroots left to draw water. The beetle larvae don’t travel farhorizontally but they do move a great deal vertically withinthe soil moisture profile. White grub populations are usual-ly found in pockets within a field.

To locate damaging populations, sift 1 row foot of soil to adepth of 12 inches at each site. Make at least one inspec-tion site per 5 acres. Randomly select sites throughout thefield. White grubs cannot be effectively controlled withapproved insecticides. Growers experiencing heavy num-bers of white grubs within fields should dig infested areasearly to avoid segregation III problems.

ThripsThrips feed primarily in terminal leaf clusters betweenfolds of young leaflets by rasping the tender leaf surfaceand sucking plant juices. This results in dwarfing and mal-formation of leaves, causing a condition called pouts. Injuryusually occurs during the first month after plant emer-gence. Systemic insecticides applied at planting controlsome thrips, but generally do not increase yields.

Thrips/Spotted Wilt DiseaseThrips are very small insects that have recently obtainedthe status of a pest insect in south and central Texas by vec-toring tomato spotted wilt virus. The resulting disease iscaused by a virus that may be transferred from diseasedplants to healthy plants by thrips.

Spotted wilt disease is spread in two different ways withina peanut field. Primary spread is caused by adult thripsinfected with the virus that fly into a field, feeding onpeanut plants and transmitting the virus. Primary spreadcannot be controlled with insecticides. Other than selectinga tolerant peanut variety, the best method of control is todelay planting until soils are warm. Peanuts planted inMarch and April require a longer growing season sinceseedlings in cool soils grow slowly and are more susceptibleto damage from spotted wilt disease. Primary spread usual-ly occurs in early planted peanuts and again when thesefields are dug and thrips carrying the spotted wilt virus flyto neighboring fields. Thrips are carried, to a large extent,by wind; therefore, it is important to plant late peanutsupwind from earlier planted fields.

Secondary spread occurs when immature thrips develop onvirus-infected plants then mature to the adult stage andfeed on other peanut plants within the same field. Thevirus can only be acquired by immature thrips feeding oninfected plants. As the thrips mature they move to otherplants nearby thus spreading the virus from plant to plant.

Limiting the Spread of Tomato Spotted Wilt VirusSeveral important factors must be considered when plan-ning a peanut production system to minimize losses due tospotted wilt disease.

■ Plant peanuts from May 20 to June 19. Surveys conduct-ed in the early 1990s show that peanuts planted withinthis time frame had less spotted wilt and produced high-er yields than earlier or later planted peanuts.

■ Insecticide use favors outbreaks of secondary pests suchas spider mites, foliage feeding caterpillars and especially

67

the silverleaf whitefly. Spider mite control is erratic withapproved pesticides. Foliar-applied insecticides destroybeneficial insects that feed on these pests, resulting inincreased numbers.

■ Foliar-applied insecticides for thrips control are not rec-ommended. Test plots show that foliar-applied insecti-cides provide erratic thrips control and only marginallyaffect the spread of spotted wilt. Certain peanut fieldsmay be seriously affected by spotted wilt even thoughprecautions on planting dates, etc., were observed. Allpeanut fields should be monitored in order to determineif spotted wilt is spreading within the field. Some fieldsmay require an insecticide treatment based on the fol-lowing procedure.

Monitoring Tomato Spotted Wilt SpreadMonitoring spread of spotted wilt helps determine how thedisease is progressing during the growing season. To moni-tor, use permanent flags to mark four rows in a field, each100 feet in length. Each row should be located near themiddle of each quadrant of the field and examined weekly.When a plant is found that appears to be infected withspotted wilt, insert a red or orange wire flag into theground beside the plant. Repeat this procedure each week,adding flags when new plants exhibit symptoms of spottedwilt. Do not remove flags until field scouting is over for theyear. By comparing the total number of plants within the100-foot sections to the number of infected plants based onthe total number of flags, the percentage of infected plantscan be determined.

Insecticides for thrips control as a treatment for tomatospotted wilt control are not suggested. The dangers of sec-ondary pest outbreaks are very real, and these pests may bemore damaging than tomato spotted wilt. However, ifsevere cases of tomato spotted wilt infection appear immi-nent, several insecticides are labeled for thrips control.

68

Granular systemic insecticides are preferred over foliarinsecticides because they are ecologically selective and lessharmful to beneficial insects on the foliage. Foliar-appliedinsecticides create worm or spider mite flare-ups moreoften than granular insecticides.

Granular materials are hazardous when wet; in-season useof these materials under irrigation systems requiring exten-sive labor and movement within the field may exposeworkers to unacceptable risks. Granular materials must befollowed by either a substantial rainfall or irrigation tobecome activated.

Lesser Cornstalk BorerThe lesser cornstalk borer is an important insect pest ofTexas peanuts. This small, slender larva is primarily a sub-terranean feeder, living beneath the soil surface in a silkentube. Late-planted peanuts are particularly susceptible todamage in the seedling stage, which often results in

69

Table 18. Insecticides for Thrips Control

Rate DaysInsecticide per acre to harvest Remarks

Temik 15G 7 lbs. 90 Apply in a band and water with center pivotsystem. May be applied through peg initiation.

Di-Syston 15G 9-10 lbs Apply in a band and water with center pivotsystem. May be applied at pegging. *

Orthene 75S 3/4 lb. 14 Apply two applications at 10-day intervals.

Thimet 20G 5 lbs. 90 Apply at planting in furrow. **

* Do not use in combination with Basagran.** Phytotoxicity could be experienced.

70

reduced plant stands. Worms injure mature plants by feed-ing on pegs, pods, stems and roots. Pegs are cut off belowthe ground surface and developing nuts are hollowed out.Stems and roots are scarred and may be girdled.

The lesser cornstalk borer is usually more harmful topeanuts grown under dryland conditions and duringdrought years. Prolonged rainfall and irrigation contributeto larval mortality. Proper timing and adequate waterapplied at each irrigation may reduce larval populations.Keeping land free of volunteer peanuts, weeds and grassesseveral weeks before planting helps reduce pest populationsduring early season.

Frequently inspect fields to determine when to treat forlesser cornstalk borer. In this way, insecticide applicationscan be timed precisely and unnecessary treatments avoided.If the producer is unable to make field checks regularly, heshould employ competent commercial field scouts for theseason.

How to Make InspectionsBegin field checks when plants emerge and continueinspections at least once a week. Select field check loca-tions at random, with one location for each 5 acres in afield with a minimum of five sample sites in any field.Select sites away from field borders. Examine soil surfacefor feeding damage, larval tubes and larvae. Later in theseason, also examine pegs and peanuts. To obtain a percentinfestation figure, divide the total number of plants inspect-ed into the number of infested plants found. Do not usedead larvae, old larval tubes or plant damage to derive aninfestation level.

ExampleFive infested plants in a total of 50 plants examined wouldbe a 10 percent infestation. If several larvae are found on asingle plant, it is counted as one infested plant.

When to Begin ControlYield or quality losses do not occur until certain infestationlevels are reached. Treatment of infestations lower thanthose indicated in Table 19 probably would not be prof-itable. In addition to the cost of the insecticide, the produc-er could destroy beneficial insects and cause problems withcertain foliage feeders and spider mites.

Treatment levels for lesser cornstalk borer in both drylandand irrigated peanuts are as follows:

Dryland Irrigated

Before initial pegging 5 percent 10 percentAfter initial pegging 10 percent 15 percent

Foliage-feeding InsectsFoliage-feeding insects include the corn earworm, vel-vetbean caterpillar, armyworm and grasshopper. Althoughthe peanut plant tolerates foliage loss, extensive feedingdamage may lower yields in both dryland and irrigatedfields. The plant is most susceptible to insect foliage dam-age at 60 to 90 days of age. Make inspections before apply-ing insecticides to determine if economically damaging

71

Table 19. Insecticides and Rates for Lesser Cornstalk Borer Control

Insecticide Rate Days Grazingto harvest and hay use

Irrigated

Lorsban15G * 71/2-15 oz/1,000 ft of row 21 No

Dryland

Lorsban15G * 71/2-15 oz/1,000 ft of row See Remarks No

Remarks - Granular Insecticides

* Lorsban 15G: Apply granules in a 14- to 18-inch uniform band over the row. If applicationsare made when plant size permits incorporation, mix granules thoroughly into the top 1 inchto 2 inches of soil. Follow application of granules with 1 to 2 acre-inches of water within 24hours. Granular insecticides are activated by moisture. Granular insecticides applied underdrought conditions may not be as effective as when applied to moist soils.

numbers of worms are present. If chemical control meas-ures become necessary, apply when worms are small.Runner type peanuts have more foliage area than Spanishtypes and can tolerate greater foliage loss before yieldreductions occur. Dryland Spanish peanut can tolerate threeto five medium-to-large larvae per linear row foot beforeyield losses occur. Irrigated Spanish peanuts can tolerateapproximately six to eight medium-to-large larvae per linearrow foot before significant yield losses occur.

Burrowing BugBurrowing bugs are soil-inhabiting insects that feed onyoung or maturing peanuts. Their feeding produces a light-to-dark brown mottling of the kernels that lowers the quali-ty grade of the crop.

Adult burrowing bugs migrate into peanut fields aroundmidsummer. They are attracted to lights in great numbers.Careful monitoring of light traps can provide useful infor-mation as to when to intensify field inspection efforts.

72

Table 20. Insects Causing Foliage Damage

GrazingRate Days to and

Insect Insecticide per acre harvest hay use

Armyworm, Asana XL 5.8 - 9.6 fl ozs., 21 Nocutworm, Orthene 75S 1 - 11/3 lb. (see remarks) 14 Nocorn earworm, Lannate L 1 - 2 pts 21 Nograsshopper Sevin 80S 11/4 - 1 lbs. 0 Yes

Velvetbean Asana XL 2.9 - 5.8 fl. ozs., 21 Nocaterpillar, Orthene 75S 1 - 11/3 lb. (see remarks) 14 Nogreen Lannate L 2 - 4 pts. 21 Nocloverworm Sevin 80S 11/4 lbs. 0 Yes

Remarks

Asana - Do not exceed 0.15 lb. of actual insecticide per acre per season. Resistance may develop.

Orthene - For grasshopper control, use 1/3 - 2/3 lb. per acre.

Burrowing bugs establish colonies soon after infesting afield. Apply insecticides when adults are detected, becauseimmature burrowing bugs are less easily controlled.Burrowing bugs can be detected by frequent field checks.Select check locations at random, with one location foreach 15 acres in a field and a minimum of five sample sitesin any field. Carefully sift through 3 row feet of soil perlocation to a depth of 4 inches. There are no apparent rela-tionships between infestation sites and soil type, topogra-phy or proximity to field borders. Do not limit inspection toa specific portion of the field.

Consider insecticide applications only after formedpods are present on plants. Early season infestations inwhich burrowing bugs feed on seedling cotyledons often donot give rise to infestation later in the season.

Miscellaneous PestsLeafhoppers and the red-necked peanut worm are frequent-ly found on peanuts. These insects are almost always pres-ent but rarely pose any threat to peanut production.Control of leafhoppers and red-necked peanut worms is notsuggested.

Other peanut pests include spider mites, silverleaf white-flies, cutworms, webworms, wireworms, corn rootworms,leaf miners, flea beetles, stink bugs and lygus bugs. If highnumbers of these pests develop, apply insecticides beforeextensive damage occurs.

The southern corn rootworm may become more of a prob-lem in wet soil with a high clay content. In some areas ofthe state, certain spider mite species in peanuts havebecome highly resistant to most organophosphate insecti-

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Table 21. Insecticides and Rates for Burrowing Bug Control

Insecticide Rate per acre Days to harvest Grazing and hay use

Lorsban 15G * 13.3 lbs. 21 No

* Has been observed to have erratic control.

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cides and cannot be controlled with registered materials inmost cases. Natural populations of beneficial organismsusually control spider mites effectively. However, frequentapplication or misuse of many insecticides and/or pesticidescan destroy beneficial organisms, thus favoring spider mitepopulation increases and development of insecticide resist-ance. Sulfur applications for leaf disease suppress spidermite populations but will not control mites when popula-tions reach economically damaging levels.

Table 22. Insecticides and Rates Controlling Spider Mites andSouthern Corn Rootworms

Days to Grazing Insect Insecticide Rate per acre harvest and hay

use

Spider mite Danitol 10.66 - 16 oz. 14 NoComite 2 pts. 14 NoOmite 3 - 4 lbs. 14 No

Southern corn Lorsban 15G* 71/2- 15 oz./1,000 row ft. 21 Norootworm

Remarks: Has been observed to have erratic control when used as a rescue treatment.

Granular insecticides

Apply granules in a 14-inch to 18-inch uniform band over the row. If application is madewhen plant size permits incorporation, mix granules into the top 1 inch to 2 inches of soil.Follow application of granules with 1 to 2 acre-inches of water within 24 hours.

Sprayable insecticides

Comite – Do not make more than one application per season.

Omite – Premix with small amount of water to form a slurry before adding to spray tank. Donot make more than two applications per season.

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Application Techniques

Field ApplicationsChemigation—(Refer to B-1652, 1990 ChemigationWorkbook, for in-depth chemigation procedures). Beforeusing this technique, consult the pesticide label for restric-tions and special instructions. Important note: Always usepressure-sensitive check valves in the injector system toprevent contamination of ground water.

Stationary systems (handlines and siderolls)—Calculatethe acreage covered in each irrigation set by multiplyingthe row length by the row width (in feet) by the number ofrows per set and divide this figure by 43,560. The amountof pesticide required per set equals the acreage covered ineach set, multiplied by the desired rate per acre of the pes-ticide.

Place the amount of pesticide required per set in the injec-tor. Before allowing the material to pass into the irrigationwater, allow time for sufficient water pressure to build andactivate all nozzles.

Consult the product’s label for information on timing theinjection in relation to total operating time per set. Forsome products, it is important to inject at the beginning ofthe set. For other products, it is equally important to injectnear the end of the set.

Moving systems (center pivots)—Determine the total areato be covered and the operating time. Place the totalamount of pesticide needed for the field in the injector tankwith sufficient water to fill the tank. Divide the total vol-ume of the tank (in gallons) by the total operating time (inhours) to give the gallons per hour at which the injectormeter should be set.

ExampleA 500-gallon injector tank is to be used for a total of 90hours operating time. Calculate the total gallons per hourby the following method:

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Total volume of tank (500 gallons) = 500 = 5.6 gal per hourTotal operating time (90 hours) 90

Now that the total gallons per hour is known, consult theinjector pump operation manual for proper meter setting.Once the system is operating, monitor the draw-down ofthe tank at hourly intervals for 3 to 4 hours to determine ifthe injector system is working properly.

Band ApplicationsBand applications place pesticides in a specific part of therow, thus reducing the amount of pesticide applied in directproportion to the ratio of the band width and row width.Failure to reduce suggested broadcast rates by this ratioresults in over-concentration of the pesticide in the bandedarea and may cause plant burn.

ExampleThe suggested broadcast rate of an insecticide is 12 ouncesper acre. The insecticide label states that application of thematerial in a 12-inch band is effective before pegging. Witha 36-inch row width, the actual amount of material appliedis reduced to 4 ounces per acre.

FormulaBroadcast rate (oz./acre) x [Band width (inches)] = Banded rate per acre

row width (inches)

Formula used with example above:Broadcast rate (12 oz./acre) x [Band width (12 inches)] = 4 oz/acre banded

row width (36 inches)

Precautions■ Read the label on each pesticide container before use.

Carefully follow all restrictions concerning use of plantmaterials as animal feed.

■ Always keep pesticides in original containers.

■ Dispose of empty containers according to label specifica-tions.

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■ Improper use of insecticides can result in poor insectcontrol as well as crop condemnation. When usingapproved insecticides, do not exceed recommended maxi-mum dosage levels, and be sure to allow the proper timebetween the last application and harvest. Using materialswithout proper label clearance, or exceeding approvedtolerance limits, can result in crop condemnation.

■ Please follow Worker Protection Standards Regulations(WPS) per label instructions for proper treatment and re-entry restrictions.

Points of Application■ Restrict insecticide use to actual need, based on field

inspections.

■ Direct hollow cone nozzles to cover plants thoroughly forfoliage-feeding insect control.

■ Nozzle size, number of nozzles, ground speed and pres-sure influence the rate of chemical output per acre.Calibrate the sprayer accurately to ensure application ofrecommended amounts of insecticide.

■ Periodically check the calibration during the season.

■ Apply insecticide sprays when weather conditions willnot cause drift to adjacent fields or crops. If showersoccur and insecticides are washed off plants within 12 to24 hours of application, the field may need to be treatedagain.

■ Maintain accurate, detailed records of pesticide use.

ReferencesBeasley, J. P. 1990. Peanut growth and development.

The Cooperative Extension Service, The University of Georgia. SB 23-3.

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The information given herein is for educational purposes only.Reference to commercial products or trade names is made withthe understanding that no discrimination is intended and noendorsement by the Cooperative Extension Service is implied.

Produced by Agricultural Communications, The Texas A&M University SystemExtension publications can be found on the Web at: http://texaserc.tamu.edu

Educational programs of the Texas Agricultural Extension Service are open to all peoplewithout regard to race, color, sex, disability, religion, age or national origin.

Issued in furtherance of Cooperative Extension Work in Agriculture and HomeEconomics, Acts of Congress of May 8, 1914, as amended, and June 30, 1914, in coop-eration with the United States Department of Agriculture. Chester P. Fehlis, DeputyDirector, Texas Agricultural Extension Service, The Texas A&M University System.M, Revision

Printing of this publication was made possibleby a grant provided by the Texas PeanutProducers Board.