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INTRODUTION TOCROP

SCOUTINGPlant Protection Programs

College of Agriculture, Foodand Natural Resources

IntegratedPestManagement

Published by MU Extension, University of Missouri-Columbia

$3.00 IPM1006

CONTENTS

Economic injury leveland economic threshold . . . . . . . . . . . . . . .3

Preparing for crop scouting . . . . . . . . . . . . . .5Developing a field history . . . . . . . . . . . . . . .6Diagnostic resources . . . . . . . . . . . . . . . . . .7

Sampling plan, recommended procedures .8Timing and frequency of sampling . . . . . . . .9Sampling patterns . . . . . . . . . . . . . . . . . . .10Number of survey stops and sampling units 11Methods of sample collection . . . . . . . . . . .12Uses of trapping . . . . . . . . . . . . . . . . . . . . .14

The scouting report . . . . . . . . . . . . . . . . . . . .15Field description . . . . . . . . . . . . . . . . . . . . .16Crop and field observtions . . . . . . . . . . . . .16Pest observations . . . . . . . . . . . . . . . . . . . .16Comments . . . . . . . . . . . . . . . . . . . . . . . . .17Field map . . . . . . . . . . . . . . . . . . . . . . . . . .17

Summary and responsibilitiesof the scout . . . . . . . . . . . . . . . . . . . . . . . .17

Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Identifying crop growth stages . . . . . . . . . .18Timeline for corn pests or pest/crop

management activities . . . . . . . . . . . . . . .20Timeline for soybean pests or pest/crop

management activities . . . . . . . . . . . . . . .21Timeline for cotton pests or pest/crop

management activities . . . . . . . . . . . . . . .22Scouting report (blank form) . . . . . . . . . . . .23

Authors

Fred Fishel, Integrated Pest Management,Department of Agronomy, University of Missouri-Columbia

Wayne Bailey, Department of Entomology,University of Missouri-Columbia

Michael Boyd, Delta Research CenterDepartment of Entomology, University ofMissouri-Columbia

Bill Johnson, Department of Agronomy, Universityof Missouri-Columbia

Maureen O’Day, Integrated Pest Management,University of Missouri-Columbia

Laura Sweets, Commercial Agriculture CropsFocus Team, Department of Plant Microbiologyand Pathology, University of Missouri-Columbia

Bill Wiebold, Department of Agronomy, Universityof Missouri-Columbia

Production

MU Extension and Agricultural InfomationDale Langford, editorDennis Murphy, designer and illustrator

© 2001 University of Missouri

This publication is part of a series of IPMManuals prepared by the Plant ProtectionPrograms of the University of Missouri. Topicscovered in the series include an introduction toscouting, weed identification and management,plant diseases, and insects of field and horticul-tural crops. These IPM Manuals are availablefrom MU Extension at the following address:

Extension Publications2800 Maguire Blvd.

Columbia, MO 652111-800-292-0969

College ofAgricultureFood andNaturalResources

select and implement a pest managementprogram. Thus, the success of the recom-mended pest management proceduresdepends on the accurate and timely comple-tion of all three crop-scouting activities. If anin-season rescue procedure is performed,crop scouts should continue monitoring thefield to evaluate performance of the pestmanagement program.

This publication explains the conceptsof the economic injury level (EIL) and economicthreshold (ET) and focuses on sampling pro-cedures. Additional publications of the MUIPM series contain crop-specific informa-tion on pest identification, and, if available,recommendations for applying the EIL andET to specific pests. Specific pest manage-ment recommendations can be found inother University Extension sources.

ECONOMICINJURY LEVEL &ECONOMICTHRESHOLD

Fields are scouted to determine whetherone or more pest management tactics arejustified. The concept of an economic injurylevel (Figure 2) was developed to provideobjective guidelines for making informeddecisions about pesticide use. The EIL is thepest density or level of crop injury that willresult in yield loss equal to the cost of man-aging the pest. It can be considered the

Crop scouting is an essential part ofIntegrated Pest Management(IPM). Integrated pest manage-

ment uses field-specific information andimproved decision-making to protect cropyield and quality while minimizing the risksassociated with pesticide use. Through a reg-ular and systematic field-sampling program,scouting provides field-specific informationon pest pressure and crop injury. This infor-mation is essential to the appropriate selec-tion and application of pest management pro-cedures. Although scouting is most oftenthought of as being a method by which rec-ommendations for in-season rescue treat-ments are made, scouting can also be used todetermine whether replanting is appropriateand to make pest management recommen-dations for the next or succeeding growingseasons (Figure 1).

Pest management professionals will useinformation provided by the crop scout to

INTRODUCTIONTO CROP SCOUTING

A well-designed scouting program includesthree main activities:

1. Sampling to provide an accurate estimateof pest densities and crop health.

2. Identification of pests or diagnosis of thecause of crop injury based on observablesymptoms.

3. Comparison of observed pest pressure orcrop injury to recommended economicinjury levels or economic thresholds.

Figure 1. Information gained by scouting fields is crucial for making deci-sions on in-season pest management treatments as well as makingdecisions about pest management in future years.

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The economic threshold is the pest den-sity or level of crop injury at which controlsshould be applied to prevent an increasingpest population from reaching the economicinjury level. The ET represents a pest den-sity lower than that of the EIL so that theproducer has time to implement the controlmeasure before the EIL is reached. The ETis often set arbitrarily at 80 percent of the EILto buffer the producer from preventable eco-nomic yield loss.

Considerable research is required toestablish the relationship between pest den-sity (or level of injury) and yield loss, so ETsare not available for all crop pests. Whenresearch-based ETs are lacking, guidelines(or nominal thresholds) may be gleaned fromfield observations of personnel with experi-ence in making pest management decisions.

Economic thresholds are more oftenavailable for insect pests than for either dis-eases or weeds. Insect biology has beenclosely studied and relationships betweeninfestation and yield loss are relatively easy todetermine. Effective insecticides that con-trol insect populations relatively quickly areavailable for most insects and crops, so treat-ment after pest identification is possible.

For most field crops, chemical controls ofpathogens are rarely used for “rescue” treat-ments. Preventive measures such as seedtreatments are more commonly used (Figure3). Few pesticides for control of diseasescaused by fungi, bacteria, or viruses are avail-able for use after the disease has becomeestablished (Figure 4). For these reasons, ETs

break-even point, or the lowest pest densityat which treatment may be economically jus-tified. The EIL is based on the economicloss caused by each pest and also the fluctu-ating values of crop market price and controlcosts. As the market value of the cropdecreases, the EIL increases. Producers willbe less inclined to control a pest as com-modity prices drop. As the cost of pest con-trol increases, the EIL increases. Moreexpensive control measures require a higherlevel of pest infestation before treatment isjustified. The EIL is independent of yieldlevel, but estimated control percentages areaffected by environmental conditions, stageof crop development, and age of the pest.Multiple pests may interact and influencethe EIL of each pest.

Integrated Pest Management4

Economic injury level (EIL) is the pest infestation point at which the costof control equals the loss of estimated crop yield. It is necessary to calcu-late these two values and compare them to know whether the economicinjury level has been reached.

EXAMPLE:Cost of control � $20/acre for material � $5/acre for application

� $25/acre

Loss of estimated crop yield:• Crop market value � $2.75/bushel• Estimated yield loss � 10 bushels/acre• Estimated control percentage � 75%

Crop market value � Estimated yield loss � Estimated control percentage� ($2.75/bu) � (10 bu/acre) � (0.75) � $20.63/acre

Because the cost of control ($25.00) is greater than the economic loss ofestimated crop yield ($20.63), this field has not reached the EIL.

Figure 3. Preventive controls such as seed treat-ments are more commonly used to manage fieldcrop diseases than in-season rescue treatments.

Economicinjury level

Economicthreshold

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Figure 2. The economic injury level is the pestdensity or level of crop injury that will result inyield loss equal to the cost of managing the pest.

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water contamination, pesticide residues infood, worker exposure to pesticides, andwildlife kills are difficult to quantify and there-fore complicate treatment decisions. EILsmay increase if potential environmentalimpacts were included in the equation as anadditional cost for the producer. Use of theEIL and ET concepts in an integrated pestmanagement system is a desirable approach tothe selection, integration, and use of methodson the basis of their anticipated economic,ecological, and sociological consequences.

PREPARING FORCROP SCOUTING

Careful preparation beforetraveling to the field improves theefficiency with which the field

can be scouted and enhances the utility of theinformation gleaned from scouting. Scoutingis part of an overall integrated monitoringplan and not a series of independent proce-dures (Figure 6). By focusing on a single pest,scouts may miss emerging problems or croprecovery from past injury. Scouts should

have been established for only a few diseasesof field crops. However, in-season applicationof fungicides is much more common forhigh-value crops such as sweet corn, seedcorn, and truck crops.

In weed management, research onthreshold levels for major weed species andcomplexes of two or more species isexpanding because of the development ofherbicide-resistant crops and associatedbroad-spectrum herbicides. Soil-applied her-bicides for control of annual grasses in cornare recommended because annual grassessuch as giant foxtail, barnyardgrass, fall pan-icum, and others are present in most fields,and corn is sensitive to early-season grassinterference (Figure 5). However, all weedsin soybeans and broadleaf weeds in corn canbe managed effectively through scouting andpostemergence herbicide selection.

EILs and ETs focus on the economicaspects of pest management and do not factorin costs once considered external to crop pro-duction. Environmental risks, such as ground-

Introduction to Crop Scouting 5

Figure 4. Pesticides for controlling diseasessuch as leaf rust of wheat should be appliedbefore the disease is well established.

Figure 5. To reduce early-season grass inter-ference in corn, soil-applied herbicides arecommonly used to control annual grasses.

Figure 6. The need for a postemergence herbicide application can bedetermined by scouting the field for weed species and densities.

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necked shape can result from corn rootwormpruning, application of a growth regulatorherbicide (Figure 9), or shallow rooting inwet or loose soil. A field record that includesthe herbicides (and rates) applied and theprevious season’s crop might possibly elimi-nate one or more of these possible causes oflodged corn.

In most situations, it is best to rely onwritten records (if available) so that the fieldhistory is not based on memory alone. Thescout should prepare the field history well inadvance of the first field visit. The initialfield visit often occurs during the plantingseason, which is a hectic time for both theproducer and the scout. Gathering all of theuseful information will be more difficult atplanting time than earlier in the season. Askthe grower to provide the following infor-mation for each scouted field:

• Specific field location and grower’s pre-ferred name or number for field identi-fication. This information will also berecorded on the scouting report and isessential to accurate delivery of informa-tion. If the producer has GPS informa-tion, record coordinates for field.

• Crops for the previous 1 to 3 years. If thefield had been planted with more thanone crop or variety in the previous year,draw a map showing locations of thecrops or varieties.

• Variety or hybrid. Specific informationincluding name/number, company, anddealer will be required so that you candetermine important characteristics (e.g.,maturity, pest resistance or tolerance,herbicide tolerance).

• Other agronomic practices such as

actively observe and record information onenvironmental conditions, beneficial insects,pest insects, diseases, weeds, crop growthstage, and the general health of the crop. Anexperienced scout knows that field and land-scape characteristics affect pest distribution,symptom expression, crop injury, and croprecovery. An integrated approach with carefulpreparation helps to anticipate and measurethe economic significance of pest and pro-duction problems and also provides a baselinefor future evaluations. Preparation includesdeveloping a thorough field history for eachfield on your route and assembling a com-prehensive set of reference materials.

Developing a field historyA complete field history provides impor-

tant clues to the accurate diagnosis of symp-toms caused by pests, nutrient deficienciesand toxicities, chemical application (Figure 7)and unfavorable environmental conditions(Figure 8). Many signs of crop injury areambiguous because similar abnormalities canhave unrelated causes. For example, cornplants lodged or growing upward in a goose-


Figure 7 (left). Root damage due to herbicide injury can resemble damagedue to soil compaction (see Figure 8, right). A complete field history mayhelp diagnose the problem and distinguish between possible causes.

Figure 9. Goose-necked corn may be due to cornrootworm pruning, growth regulator herbicideinjury, or shallow rooting in wet or loose soil.

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recover from, pest damage is often influ-enced by its growth stage. For example, yieldloss from defoliation of soybean plants isgreater for R5 plants than for V4 plants(Figure 11). Conversely, the economicthreshold for black cutworm damage to corntypically increases as the crop developsthrough the early vegetative stages so thatblack cutworm is rarely of economic conse-quence after the V5 (five leaf) stage.

References to be used in identifying pestsor crop abnormality should contain high-quality photos and descriptive keys. Variousstages of pest development should be illus-trated. Weed references should focus impor-tant weed seedling characteristics such asligules (Figures 12–15) and leaf shapes. Insect

planting date, planting rate, row width,and tillage operations; timing of tillage(i.e., fall or spring) may also be useful.

• Pesticide names, rates, and applicationdates. Note whether or not seed treat-ments were used and whether they wereapplied by the seed company or by theproducer. Because of potential carryoverof herbicide effects, record informationfor herbicides applied the previous season.

• Weather patterns of the present and pre-vious season (including winter).

• Fertilizer and lime application rates andmethod of application.

• Soil test results, including N, P, K, per-cent organic matter, and pH.

• Soil type.• Irrigation availability.• Previous pest problems.

Diagnostic resourcesWell-prepared scouts assemble a set of

reference materials for interpreting the infor-mation collected during field visits. Some ofthese materials can and should be carried tothe field site. Others are useful for study bothbefore and after the field visit. Other publi-cations that are part of the MU IPM series areparticularly helpful for Missouri-based scouts.

Scouts must be able to recognize theappearance of a healthy crop plant, includingthe root system (Figure 10), before they candiagnose departures from the norm. It is alsoimportant to know how to stage a crop,because its susceptibility to, or its ability to


Figure 10. The corn plant at left, injured by her-bicide carryover, shows reduced above-groundand root growth. Healthy plant at right.

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Figure 11. The stage of growth of a crop can influence its susceptibilityto pest damage or its ability to recover. Yield loss due to defoliation isgreater when defoliation occurs at the R5 growth stage than the V4 stage.

Figures 12–15. The collar region of grassy weeds contains subtle keysto their correct identification. Smooth crabgrass (top right) has a mem-branous ligule; fall panicum (above left) has ring of hair. Barnyardgrass(middle) has no ligule. Auricles are fingerlike clasping structures in thecollar region of quackgrass and the ryegrasses (above right).

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SAMPLING PLAN,RECOMMENDEDPROCEDURES

The purpose of scouting is to determinewhether a pest is present and if the applica-tion of a pest management procedure is jus-tified. Scouting is also beneficial to deter-mine whether nutrient deficiencies, soilcompaction or other disorders are affectingcrop health. It is not practical to observeevery plant within the field, so fields are sam-pled to estimate the level of infestation. Thechallenge of sampling is to balance the accu-racy of estimates with the time and laborrequired to collect the samples. Although thereliability of estimates increases as samplesize increases (up to a point), the collectionof too large a sample is costly and inefficientand it wastes human resources.

The sampling plan is the procedure forobtaining a sample to estimate the populationof one or more pests or the degree of cropinjury in a field. The plan includes the timingof sampling and the directions for: (1) spatialdistribution of survey stops, (2) the numberof survey stops, (3) and the size or composi-tion of the sampling unit at each survey stop.The magnitude or composition of subsam-ples from a single inspection or survey stopis called the “sampling unit.” A “survey stop”is the area of the field in which a single sam-pling unit is inspected, counted, or collected.The total number of observations from allsurvey stops is referred to as the “sample.”For example, if the sampling unit consistedof 20 sweeps with a sweep net, 10 surveystops would require 10 sets of 20 sweeps each,or a sample size of 200 sweeps in the field.Likewise, if the sampling unit consisted ofinspecting 20 corn plants for black cutwormdamage, 10 survey stops would requireinspection of 10 sets of 20 plants each, for asample size of 200 plants.

references should include progressive stagesof growth. Many insect pests, especiallylarvae, change their color as they develop.Because an insect pest’s feeding habits or col-oration may make it difficult to find in thefield, it is helpful to have diagnostic aids basedon symptoms of crop damage. Insect refer-ences should also include beneficial insects.

Plant disease references should illustrateor describe symptoms on all affected plantparts. Many diseases exhibit both above- andbelow-ground symptoms. Signs, or evidenceof the pest itself, may provide clues for thediagnosis of infectious diseases. Symptoms ofnutrient deficiency or toxicity as well as dis-eases with other abiotic origins should beincluded (Figure 16). All references shouldinclude characteristics or diagnostic tips nec-essary to distinguish among abnormalitiesthat exhibit similar symptoms or pests thatappear similar. A “compare and contrastformat” may help distinguish subtle differ-ences in symptoms.

See MU publication MP730, A Guide toDiagnostic Services, for detailed instructionsand forms for submitting samples to the fol-lowing clinics and laboratories: PlantDiagnostic Clinic (diseases, insects, plants orweeds), Plant Nematology Laboratory, andSoil and Plant Testing Laboratory.


Figure 16. Scouts should make note of any abiotic disorder theyencounter in the field, including lightning damage (shown here) ornutrient deficiencies.

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of overwintering insects will be useful indetermining when fields should be scouted.For example, scouting for first-generationEuropean corn borers in mid-Missouri shouldbegin 200 degree-days, or approximately 11to 12 days, after the first spring-flight mothhas been detected by trapping or flushingfrom action sites in grassy field margins.

Crop stage of developmentMonitoring of the crop growth stages

most vulnerable to key pests may also be usedto determine timing of sampling because theremust be synchrony between the injurious stageof the pest and the vulnerable stage of thehost crop. For example, the alfalfa weevil(Figure 17) is sampled before first hay-cuttingbecause the larvae do not cause economiclosses to subsequent growth. Some pests favorcertain crop stages of development. Femalestink bugs are highly attracted to soybeansonce the plants start to bloom, so sampling oflate-instar nymphs and adults should begin atthat time. Spring-flight European corn borerfemales are more attracted to taller, early-planted corn, whereas summer-flight mothsprefer to deposit their eggs during pollen shedin late-planted cornfields with fresh silks.Based on stage of development or plantingdate, those cornfields most likely to sustaininjury should be given first priority for sam-pling European corn borers.

WeatherWeather conditions not only affect the

crop susceptibility to damage, but also influ-ence the development of pests or the expres-sion of symptoms from abiotic agents.Flushes of weed emergence for severalspecies, including waterhemp, may occurafter rainfall. The expression of sudden deathsyndrome symptoms in soybean fields is oftentied to wet soil conditions 2 or 3 weeks pre-vious. Potassium deficiency symptoms aremost likely to occur in dry soils. Droughtconditions increase the likelihood of injuryfrom spider mites (Figure 18), corn leafaphids, or grasshoppers (Figure 19). Rainfallor high humidity during anthesis of wheat is

Timing and frequency of sampling

Sometimes it is challenging to determinewhen sampling for pests should begin. Theinefficiency of sampling before sufficientnumbers of pests are present must be bal-anced against the risk of sampling after aninfestation has caused significant crop loss.Knowledge about pest biology and cropgrowth will help determine when samplingshould begin and how frequently the fieldshould be visited. Monitoring weather con-ditions will help in the prediction of bothpest and crop development. Informationincluded in the field history such as agro-nomic practices will help focus attention onkey pests. Information from trapping pro-grams (e.g., black cutworm or European cornborer) will also provide information on whento scout for specific pests.

Pest biologyRecommendations for initiating sam-

pling for some insect pests are based on cal-endar dates because the timing of importantdevelopment stages of such pests are more orless consistent among years. For example,predictions regarding the adult emergence ofcorn rootworm and pecan weevil are oftenbased on calendar dates because their devel-opment occurs in the soil at relatively con-stant temperatures. The development ofother insect pests as well as most diseaseorganisms and weeds is so dependent onweather conditions that calendar dates shouldbe used only as rough guidelines for the ini-tiation of sampling.

Some key insect pests and disease organ-isms overwinter in the coastal areas of theGulf of Mexico and migrate north to theMidwest each spring. The timing and trajec-tories of annual pest migrations can be pre-dicted by monitoring complex atmosphericcirculation patterns or even persistent air-flows from specific directions; but these rela-tionships are complicated and beyond thepractical applications for most scouts. Beingaware of, and perhaps participating in,areawide trapping programs that monitormigration, as well as the seasonal emergence


Figure 17. Sample foralfalfa weevil beforefirst hay-cutting; thepest does not causeeconomic losses onlater growth.

Figure 18. Droughtconditions increasethe likelihood ofspider mite infesta-tions.

Figure 19. Droughtconditions may alsolead to an increasein the number ofgrasshoppers.

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to obtain an unbiased estimate of the pestpopulation or crop injury. However, a patternof unrestricted random sampling could resultin placement of the majority of the surveystops in the same area of a field. To correctfor that possible error, restrictions to thesampling pattern are imposed. These restric-tions help ensure that all areas of the field aresampled.

The most common pattern in scoutingprograms involves walking along a predeter-mined zigzag or M-shaped route through afield (Figure 20). This pattern is commonlyused because it is easy to teach, convenient touse, and ensures that all regions of the fieldare visited.

Before the scout arrives at the field, thepattern should be drawn on a field map. Eachsurvey stop should represent approximately5 to 7 acres. Use this relationship to deter-mine the number of survey stops. Forexample, a 50-acre field would require 7 to 10survey stops. The approximate placement ofeach survey stop should be marked on thedrawing. However, these placements maychange slightly to prevent too many of thesurvey stops from falling on some patternresulting from an agronomic practice (e.g.,sprayer overlap).

When approaching the first plant (orarea) of each survey stop, the scout should notbe looking at the crop. Many scouts are subtlybiased toward selection of a damaged plant or

nearly essential to the development of scab.Weather conditions the previous fall andwinter may also be important. Winter annualweeds are most likely to be a problem after awarm winter. Insect and disease organismpopulations may also increase as a result ofwarm winters.

The growth rates of many insects andseveral crop plants depend on ambient tem-perature. Degree-day models, which relatetemperature and pest population develop-ment, are an integral component of cost-effective scouting programs because theyhelp to time sampling efforts accurately.Degree-day projections forecast when a pop-ulation will reach a certain damaging stage,such as the “cutting” stage of black cutworm(Table 1) or the “tunneling” stage ofEuropean corn borers. An event in theinsect’s life cycle may trigger the accumula-tion of degree-days, such as the first signifi-cant flight of migratory pests into a locale(black cutworm) or first detection ofemerging adults from an overwintering pop-ulation (European corn borer). For otherpests like alfalfa weevil, January 1 is the arbi-trary base starting point for accumulatingdegree-days to predict larval hatch becauseeggs are laid in the fall over a prolongedperiod.

Sampling patterns

The sampling pattern will dictate whereeach of the survey stops will occur. Becausesampling is performed in order to estimatethe degree of pest infestation or the amountof crop injury, it may seem appropriate to usea completely randomized scheme in whicheach subdivision in the field would have anequal chance of selection, enabling the scout


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Figure 20. The most common pattern inscouting involves walking along a predeter-mined zigzag or M-shaped route through a field.Table 1. Black cutworm development and activity as influenced by degree-days.

Stage Activity Degree-days

Egg hatch 90

1st – 3rd instar Leaf pinhole feeding 91 – 311

4th instar Initial cutting 312 – 364

5th instar Plant cutting 365 – 430

6th instar Cutting slows 431 – 640

Pupa – adult Cutting stops 641 – 989

are covered; for example, alternate a zigzagpattern with an M-shaped pattern. Avoidsampling in the same areas of the field oralways entering the field at the same point onsuccessive sampling visits.

Number of survey stops andsampling units

The exact number of survey stops andsampling units inspected, counted, or col-lected at each survey stop may be influencedby the pest, its spatial dispersion, the type ofcrop injury, and other factors. Detailed sam-pling protocols for some key pests can befound in the MU IPM publication series.The following is a generalized scouting pro-tocol, but keep in mind that unbiased popu-lation estimates for specific pests may requiremore intensive sampling. Conversely, labor-intensive or costly sampling methods maynecessitate fewer samples.

A field size of 50 acres is generallyaccepted as the maximum land area to scoutas a unit. Large fields should be divided intosmaller subdivisions equal to or smaller than50 acres for scouting. Landscape character-istics and information from the field historycan be used to subdivide the field. Fieldsshould be divided into even smaller subdivi-sions if areas of the field have been under dif-ferent management systems. For example, ifa 50-acre cornfield had been planted to 25acres of corn and 25 acres of soybeans theprevious season, the field should be scoutedas two separate 25-acre fields dividedaccording to last year’s crop history.Regardless of size, fields planted with two ormore varieties should be scouted as variety-specific subdivisions. If the field has consid-erable topographic or soil variation, thenumber of survey stops should be increased,especially if the pest population or percentageof crop injury approaches the economicthreshold.

Characteristics of a pest and the mannerin which the pest interacts with the environ-ment determine how individuals of the pestpopulation will be dispersed throughout thefield. Because the microclimate varies within

area of the field. While looking away fromthe crop, walk 10 steps forward, and begin thesample unit with the plant nearest your rightfoot. Sample consecutive plants in eachsample unit if the target insect will not be dis-turbed by sampling adjacent plants. If thepest is mobile or easily startled, take severalsteps between plants and sample randomly toavoid underestimating the pest populationcounts. For example, corn rootworm beetlesare easily disturbed and may rapidly dropfrom the plant to the ground. Repeat thesame selection process for each survey stop.When walking between survey stops, remainalert and make notes of observed pest prob-lems, crop damage, and field conditions suchas soil moisture.

Cover the entire field during eachscouting trip. Avoid field margins and borderrows unless there are specific reasons formonitoring the edges of the field. To coun-teract any “edge effect,” go into the field atleast 40 rows or 100 feet before inspecting,counting, or collecting the sampling unit.Edge effect is the tendency for several keyinsect pests to cluster near the field margin.Sampling near the edge of the field tends tooverestimate the densities of many insectpests. Exceptions to the rule include delib-erate survey stops in the outer rows of a corn-field adjacent to maturing small grains tomonitor the invasion of true armyworms orchinch bugs (Figure 21).

On return visits to the field, change thesampling pattern so that all areas of the field


Figure 21. For pests such as chinch bugs, it maybe necessary to sample near the edge of fields.

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Methods of sample collection

Procedures for sampling units are variedand are often pest/host specific. Many of therecommended procedures involve directobservation of the pest. Most weeds andmany insect pests are sampled in this manner.Pest densities are counted and recorded onthe survey form as the number of pests perplant, sampling activity (e.g., sweeps), rowlength, or unit land area. Some insects can bedifficult to observe because of their smallsize, so a magnifying lens may be required.This lens is also useful for identifying closelyrelated weeds.

Sometimes, to expedite sampling, only aspecific portion of the plant is examined.Insects may be observed on a specific plantpart because the pest has a preferred site onthe plant for feeding or egg-laying (Figure23). Scouting for second-generationEuropean corn borers involves examiningleaves in the “ear zone” (middle seven leavesof the reproductive-stage corn plant) for eggmasses. In addition, if a pest typically injuresan economically important product (e.g.,corn earworm on sweet corn), that part of theplant is specifically observed (Figure 24).

Some insects are easier to count if theyare dislodged from the plant by vigorousshaking and allowing the insects to fall intoa bucket or onto a white “beat sheet.” This

nearly every field, few pests are randomlydistributed within a field. Both pest and fieldcharacteristics will affect the degree of aggre-gation (Figure 22). In general, as the degreeof aggregation of the pest populationincreases, the number of survey stopsrequired for a reliable estimate of the popu-lation increases. In addition, as aggregationincreases, the number of survey stopsexhibiting few pest numbers or minimal cropinjury increases. This does not mean a pestis not present or is not causing injury.

Each sampling unit involves a specificnumber of plants, actions (e.g., 20 sweepswith a net), or land area (e.g., 100 square feetfor weed scouting). Composition of the sam-pling unit is pest and often crop specific.Time and labor requirements help determinespecific protocols. For example, visuallyexamining 20 corn seedlings for black cut-worm damage requires less time and effortthan unfurling the leaves of 10 whorl-stagecorn plants or splitting 10 stalks to assess thelevel of European corn borer infestation. Asa general rule, it is better to make moresurvey stops consisting of fewer samplingunits than smaller survey stops consisting oflarger sampling units. For example, 10 surveystops of 10 sweeps each are superior to 5survey stops of 20 sweeps each, even thoughthe sample size would be equivalent.


Random ClumpedFigure 22. Pests may be present in differentdispersion patterns within a field, affecting thesuccess of detection.

Figure 23. Careful inspection may be needed todetect the presence of some pests.

Figure 24 (inset). Sampling may be targeted tothe part of the plant most likely to be damagedby a certain pest; for example, checking sweetcorn ears for corn earworm.

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counting is sweeping with a sweep or butter-fly net. This technique is often used to esti-mate populations of potato leafhoppers inalfalfa or defoliating insects in drilled soy-beans (Figure 26). Some scouts find it helpfulto abruptly thrust the net upward on the finalswing to force net contents into the bottomof the net, quickly turn the top (hoop) of thenet sideways to block escape while grabbingthe lowest quarter of the net from the out-side, and force the swept contents into agallon-size plastic bag. This technique min-imizes escapes, allows easier counting ofinsects, and reduces the number of stingsfrom agitated nontarget insects. Althoughsweeping can capture many insects with min-imal labor and crop damage, the efficiency ofthis method varies with the insect species,crop height, time of day, weather, andsweeping technique. Sampling data are gen-erally reported on the scouting report as theaverage number of insects per sweep.

Some pests live or cause damage under-ground, so digging up soil cores or a portionof the root mass may be required for obser-vation. (Figure 27). Populations of plant-par-asitic nematodes are sampled by collectingmultiple soil cores with a cylindrical probe toa depth of 6 to 8 inches. Soil samplesremoved from close proximity to the plantare sometimes collected to detect the pres-ence of corn rootworm larvae and to estimatethe stage of development. The reliability ofthis technique is questionable because it isdifficult to control the dimensions of the soilsample with a shovel. Custom-made and

technique is especially effective in countinginsects with coloration that blends with thecrop foliage. Soybean looper and greencloverworm, for example, can be counted farmore easily if seen against the white back-ground of the beat sheet than on soybeanfoliage. The cloth should be carefullyunrolled on the ground and placed betweentwo 30-inch rows in a soybean field; plants onboth sides of the row are then vigorouslyshaken to dislodge insects (Figure 25). Otherpests are well concealed by parts of the hostplant. The entire stem of an alfalfa plant orthe head of a sorghum plant can be vigorouslybeaten into a large white bucket for dis-lodging and estimating the number of alfalfaweevils or sorghum headworms, respectively.The success of “beating methods” obviouslydepends on the extent to which the targetpests release their grip on the infested plants.Another method of dislodging insectsinvolves the use of an aspirator in whichinsects are sucked into a container for lateridentification.

A common method for “capturing”insects in the field for identification and


Figure 25. Some pests are easier to count if a“beat sheet” is placed on the ground beforeplants are shaken to dislodge the insects.

Figure 26. Sweeping with a sweep net or butter-fly net is a common method of capturing insectsin the field for identification and counting.

Figure 27. Soil coresare used to detectsoil insects or plantparasitic nematodes.

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damaged reproductive structures. When theobjective of sampling is to determine theneed for a rescue treatment, direct estimatesof pest density are also necessary to ensurethat the pest is still damaging the crop. Evenif the level of crop damage exceeds the eco-nomic threshold, avoid recommending a“revenge” treatment if the insect pest is nota current threat. The pest may have migratedfrom the field in search of a more suitablehost plant, or may still be present but heavilyparasitized (Figure 29) or near pupation.

The recommended sampling method fora particular pest on a crop may differaccording to the growth stage of either thepest or the crop and even the canopy struc-ture of the crop. For instance, early in theseason, direct counting over a measuredlength of row is the most practical method forsampling bean leaf beetles on soybeans. Afterthe V4 stage, the sweep net in drilled soy-beans or the “beat cloth” (with a row spacingof 30 inches) provides more reliable popula-tion estimates.

Uses of trappingAs described earlier, trapping of insects

can help determine timing strategies for fieldscouting. In most instances, trapping is per-formed in conjunction with other scouts orwith oversight by public agencies. Contactthe local extension office for access to insecttrap information. Trapping may help reducethe variation associated with the differentsampling techniques of scouts and may

commercially available tools can increasesampling accuracy.

Destructive sampling of plant tissue isnot frequently required as part of the directobservation, but sometimes plant parts mustbe cut, split, or partially dug up to confirmthe presence of a pest. Sampling for first-generation European corn borers requirespulling the whorls from knee-high to pre-tassel stage corn and unfurling the leaves tocount young larvae feeding between theunexpanded leaves.

The diagnosis of plant diseases is oftenbased on symptoms and field distributionbecause the small size of the pathogen ininfectious diseases and the absence of apathogen in noninfectious diseases (e.g., frostinjury or nutrient deficiency) make directobservation nearly impossible. For someinfectious diseases, signs (i.e., evidence of theactual pathogen such as fungal fruitingbodies) are also important clues. Obser-vations for diseases are recorded on thesurvey form as either the number of plantsexhibiting symptoms or the proportion ofplant parts affected by the disease (e.g., per-centage of wheat flag leaf infected with rust).

When scouting for insects, the symp-toms or signs of crop injury are often moreconspicuous than the insect pest causingthem. Several insect pests are primarily noc-turnal feeders and so may not be visibleduring the day. During black cutworm sur-veys, for example, the scout should be alertfor clues such as cut corn leaves partiallyburied in burrows. Occasionally, sample col-lection may include a unit measure of by-products of insect feeding or inhabitation;examples include the amount of frass (Figure28), number of egg or pupal cases, or nests ofcolony-forming caterpillars such as the fallwebworm.

Sometimes crop injury is the factor thatis observed and upon which economicthresholds are based. Crop injury estimatesare recorded on the scouting form as adescription of the injury such as percent defo-liation, number of pruned roots, percent ofdamaged stem terminals, or proportion of


Figure 28. Whensampling for insectproblems, it may benecessary to recordlevels of insect by-products such asinsect frass.

Figure 29. Scouts should note whether pests areparasitized or near pupation. This hornworm isinfested with parasites.

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Traps that lure insects through therelease of pheromones are highly selective tothe target insect. For this reason, sortingbefore counting the target pest is rarely nec-essary (Figure 31). Insects for whichpheromone traps have been successfully usedinclude black cutworm, European corn borer,gypsy moth, and boll weevil. Solar bait sta-tions (Figure 32) are used to monitor wire-worm populations and are an example ofattraction with odors associated with food.

The scouting report is often the onlyrecord of the field sampling survey. Althoughscouts may have the opportunity to reportsampling information orally, the scoutingreport can be filed and saved whereas oralcomments cannot. It is imperative that thescouting report accurately communicateswhat was found and the methods used toobtain the information (Figure 33). A com-plete and legible scouting report is the essen-tial “road map” guiding pest managementdecisions. Over the course of several growingseasons, scouting reports provide a perma-nent record and time line of pest activity andcrop growth. Such detailed records can leadto improved management strategies for theentire field and site-specific locations withinthe field. An example of a scouting report thathas been properly completed is shown in

reduce the diurnal and weather-related vari-ation that affect sampling results from eachweekly field visit. However, trapping shouldnot replace in-field sampling.

The most common insect traps attractinsects with visual clues, pheromones, or foododors. The short-wavelength light used inblacklight traps (Figure 30) is an example ofattraction with visual clues. This method isespecially effective for attracting several eco-nomically important nocturnal insects.Blacklight captures do not provide samplingestimates, but indicate when to beginscouting based on initial or peak flight. Firstcaptures of European corn borer moths, forexample, indicate that the females will soonbegin to deposit egg masses in nearby fields.Blacklight traps are labor-intensive becausethey are nonselective. They indiscriminatelycapture many flying insects in large recepta-cles, and the target insects must then behand-sorted from large numbers of othersbefore counting. The strong attraction ofmany insect species to color has beenexploited in the design of traps. Many aphids,Japanese beetles, and corn rootworm beetlesare attracted to yellow. In cornfields, yellowsticky traps may be placed at ear height toestimate populations of corn rootwormadults. These traps provide more reliableestimates than direct visual counts because ofthe propensity of the beetles to startle easilyand drop to the ground when scoutsapproach an infested plant.


Figure 30. A blacklight insect trap uses a short-wavelength light to attract insects.

Figure 31. Wing-style pheromone traps can beused to monitor coddling moths or other lepidop-terous pests in orchards.

Figure 32. Solar baittraps can be used todetect wireworms.

Figure 33. Detailedscouting reports areneeded for judiciouspest management.

THE SCOUTING REPORT

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scout and the producer. If the producer hasGPS information, record the coordinates forthe field. If the information will be enteredinto a database for record keeping, add aunique ID in addition to the field descriptorfor the farmer and a customer ID. If the fieldwas divided into two or more portions fill outa separate survey form for each portion andrecord the acreage of each. In this instanceuse similar or linked identifications so thatmultiple reports can be reviewed together.Information for the variety or hybrid shouldbe specific and include the company name aswell as the variety name or number. Afterarriving at the field, record the date and time.

Pest observations (B)The pest or description of crop damage

should be reported with the sampling unit —for example, square feet of area inspected,number of plants dissected, or sweeps col-lected. The counts or estimates should beentered separately for each survey stop.Accurately calculate the average or per-centage of pest density or crop damage in theinsect and disease sections of the scoutingreport. The procedure for weed scouting andyield loss tables based on weed density andcrop and weed height are included in PracticalWeed Science for the Field Scout: Corn andSoybeans (IPM 1007). Enter the stage of pestdevelopment (if it may factor into a manage-ment decision) and the average height andnumber of leaves for the weeds that arerecorded. If there is doubt as to the correctidentification or diagnosis, collect samplesof pests or damaged plants for later confir-mation of the pest or cause of the symptoms.

Crop and field observations (C)As the sampling plan is followed, record

the following information in the area pro-vided near the bottom of the form: cropgrowth stage; crop height (useful for weedcontrol recommendations); soil conditions(moisture, crusting, etc.); weather conditions(approximate temperature and wind speed;sunny, cloudy, or rainy).

Record all plant counts so that the

Figure 34; boldface capital letters in the fol-lowing paragraphs are keyed to specific areasof the completed form. A blank report formis provided in the Appendix. The MissouriScouting Form contains five categories ofinformation: field description, crop fieldobservations, pest observations, comments,and field map.

Field description (A)The top portion of the scouting report

should be filled out before entering the field.Some of this information was gathered whenthe field crop history was developed. Thefield ID should be understandable to both the


A

B

C

E

D

Figure 34. Sample scouting report. Letter blocks refer to the followingparagraphs.

either the producer or pest management pro-fessional. This additional information couldinclude: other pests and the approximate levelof crop injury between survey stops; benefi-cial insects and their abundance; more detailson recorded pests (e.g., “25% of armywormsparasitized”); or unusual field conditions(e.g., “standing water in NE corner”).

Field map (E)Before arriving at the field, the sampling

pattern including the location of each surveystop should have been drawn in the spaceprovided. Record landmarks, roadways andother pertinent information to help withorientation on this map.

number of plants per acre can be estimated.Wait to count plants for this purpose untilmost seedlings have emerged, about twoweeks after emergence was first noted. Referto MU publication G4091, Corn and SoybeanReplant Decisions, for recommended methodsfor estimating plant populations. For cropsplanted in 15- to 40-inch rows, record therow length used for each plant count. For rowspacings less than 15 inches, use hula-hoopsor some other rigid frame. Record the diam-eter or area of the hula-hoop.

Comments (D)Use the comments section to record

additional information that may be useful to


SUMMARY and RESPONSIBILITIESof the SCOUT

Crop scouting is an integral part of integrated pest management; the crop scout isan essential partner in programs designed to protect crop yield and quality whileminimizing the risks associated with pesticide use. Scouts should not make pest man-

agement recommendations. Pest management professionals will use the scouting report to selectand implement pest management programs. Thus, the success of the recommended pest man-agement procedures depends on timely field sampling and accurate communication of gath-ered information. It is the responsibility of the scout to

• Be familiar with the concepts of economicinjury level and economic threshold and beable to apply these concepts to importantcrop pests.

• Use advance planning to prepare for fieldvisits including developing field histo-ries gathered through interviews withproducers.

• Be knowledgeable of self-limitations andknow locations of information sourcesrequired to make accurate diagnoses;these sources include written documents,electronic documents, and diagnosticlaboratories.

• Understand the purposes of field sam-pling and the limitations of recom-mended protocols.

• Follow recommended procedures, but be

flexible in response to site-specific vari-ables.

• Understand the manner in which pestbiology, crop plant development,weather, field characteristics, and agro-nomic practices interact to influence pestdevelopment and expression of injury.

• Use the best sampling methods and beaware that these methods are oftenpest/host specific.

• Know how trapping can benefit fieldsampling.

• Accurately complete the field scoutingreport.

• Use language that accurately communi-cates information to producers and pestmanagement professionals.

• Keep records for future reference.

leaf is one that has a leaf above it withunfolded leaflets. A V2 plant has unfoldedleaves on three nodes (1 unifoliolate and 2 tri-foliolate).

Reproductive stages are designated R1through R8, which describe flowering (R1and R2), pod development (R3 and R4), seeddevelopment (R5 and R6), and maturity (R7and R8). At R1, one open flower is found onthe main stem while a plant with an openflower at one of the two uppermost nodes onthe main stem with a fully developed leaf isin R2. An R3 plant has a 3⁄16-inch-long pod atone of the four uppermost nodes on the mainstem with a fully developed leaf. When oneof the uppermost nodes has a pod thatreaches 3⁄4 inch long, the plant is in R4. TheR5 stage has pods with seeds 1⁄8 inch long inone of the four uppermost nodes on the mainstem with a fully developed leaf. However,when the green seed fills the pod cavity at oneof the four uppermost nodes, the plant is inR6. Physiological maturity (R7) occurs whenone pod on the main stem has reached itsmature (brown or tan) color. Full maturity isattained (R8) when 95% of the pods havereached their mature color.

WheatFeeke’s scale is commonly used to

describe the developmental stages of wheat.It consists of 11 leaf stages of grain develop-ment. One shoot (stage 1) and tillering (stage2) up to erect leaves with three tillers (stage5) encompass leaf and tiller development.Wheat is dormant during stages 2 and 3.Stem elongation occurs from stage 6 to stage10. At stage 6, the first node is visible(jointing), followed by the second node (stage7). When the last leaf (flag leaf) is visible (justthe leaf, not the ligule), wheat is at stage 8.When the ligule of the last (flag) leaf is vis-ible, it is at stage 9. The boot stage (10) con-cludes the stem elongation development ofwheat. Flowering occurs at stage 10.5, andstage 11 is grain development.

Grain sorghumGrain sorghum stages of development

Identifying crop growth stagesWhen determining the growth stage of

a crop, be sure to observe plants throughoutthe field, because variation occurs within anyfield. A field or sample is said to be at a cer-tain stage of development when 50 percent ofthe plants in the field are at that stage. Corn,soybean, and rice development is divided intovegetative (V) and reproductive (R) stages.

CornSubdivisions of the vegetative stages for

corn are designated numerically as VE(emergence), V1 (one visible leaf collar), V2(two leaf collars visible), and so forth. The lastvegetative stage (VT) occurs when the lasttassel branch is completely visible.

Reproductive (R) stages are designatedR1 through R6. R1 (silking) occurs whensilks are visible outside of husks. R2 (blister)is when the liquid in the kernel is the colorand consistency of a blister. The endospermturns white and becomes thicker as solidstarch is deposited. R3 is designated as themilk stage, and R4 is designated as the doughstage. A dent (R5) forms at the tip as thecenter of the kernel collapses because ofshrinkage. After R5, a “milk line” forms andmarks the layer between solid and liquidstarch in the endosperm. Physiological matu-rity (R6) occurs when kernels have obtainedtheir maximum dry weight and an abscissionlayer (black or brown) forms near the bottomof the kernel.

SoybeansVE designates soybean emergence and

occurs when cotyledons are visible above thesoil. VC designates the cotyledon stage andoccurs when the unifoliolate leaves are fullyextended. To determine all other vegetativestages, counting the node where the unifoli-olate leaves are or were attached and continuecounting until you reach the uppermost nodewith a fully developed leaf. A fully developed


APPENDIX

in diamter at the fifth to eighth node. Firstflower occurs when there are 12 to 16 nodes.Cutout typically occurs when there are fivenodes or less above white flower (NAWF).First open boll occurs 45 to 60 days afterfirst flower. Cotton is harvest ready when 95percent of the harvestable bolls are open.

RiceRice growth stages are designated as

seedling (S), vegetative (V), and reproductive(R). Seedling growth stages (S0 to S3) occurbefore rice emerges. Vegetative: Emergenceis when the coleoptile is visible above thesoil surface. Formation of the first leaf collaron the main stem signifies the V1 stage. Vstages continue as new leaf collars are addedto the main stem until V13, which is usuallythe flag leaf stage. There are 10 reproductivestages. Reproductive stages R0 (panicle ini-tiation) and R1 (branches on panicle) beginbefore flag leaf development (V13) V13 andR2 both signify that the flag leaf collar is vis-ible. At R3, the tip of the panicle is visibleabove the collar of the flag leaf. At R4, oneor more of the florets on the main stem pan-icle has reached anthesis. R5 and R6 indicatecaryopsis elongation on the main stem pan-icle. At stages R7 and R8, one grain on themain stem panicle has , respectively, a yellowor brown hull. At R9, all grains that havereached R6 have brown hulls. A DD-50 com-puter growth model is often used to predictgrowth stages.

have been assigned numbers from 0 to 9.Stage 0 is when the shoot (coleoptile) is vis-ible at the soil surface. Stages 1 and 2 desig-nate a visible leaf collar at the third and fifthleaves, respectively. Stage 3 (growing pointdifferentiation) occurs when the growingpoint changes from vegetative to reproduc-tive and there are 7 to 10 leaves visible. Atgrowth stage 4, the final or flag leaf is visiblein the whorl and all but the final three to fourleaves are fully expanded. At growth stage 5(boot), the sorghum head is nearly full sizeand enclosed in the flag leaf sheath. Growthstage 6 (half-bloom) occurs when half theplants in a field or sample are in some stageof bloom. Stage 7 (soft dough) and 8 (harddough) are similar to that described for cornor rice. Stage 9 (physiological maturity) canbe determined by the presence of a dark spoton the opposite side of the kernel from theembryo. Grain moisture is 25 to 35 percentat maturity.

CottonCotton vegetative growth is designated

by leaf stages. The cotyledon stage is whenonly the cotyledon leaves are present. A leafstage occurs when there is a fully unfoldedleaf at least 1 inch in diameter (or roughly thesize of a quarter). The fifth leaf stage has nosquares present and five fully unfolded leavesat least 1 inch in diameter above thecotyledon leaves. For the reproductive stages,first square is when there is a square 1⁄8 inch



1 This timeline is estimated for central Missouri. For the northern third of the state, advance timeline by 2 to 3 days. For the southeastern “Bootheel,” move the timeline back by 10 days.

Timeline for Corn Pests or Pest/Crop Management Activities for Central Missouri 1

P e s t(or crop management activity)

A p r i l M a y J u n e J u l y A u g u s t S e p t . O c t .

Seedling decay, Seedling blights

No-till winter/early-spring weeds

Early-season weed control

Determine plant stands

Nematode symptoms

Seedcorn maggot, Seedcorn beetles

Wireworms, White grubs

Corn flea beetle

Stewart’s wilt

Grape colaspis – larvae

Black cutworm

Sod webworm

Southern corn leaf beetle

Chinch bug

Armyworm

Stalk borer

European corn borer (1st gen.)

Southwestern corn borer (1st gen.)Corn rootworms – larvae

Late postemergence weed control

Weed mapping and assessingoverall weed control

Gray leaf spot, Common rust,Southern rust, Other foliage diseases

Corn rootworms – adults

Grasshoppers

Fall armyworm

Corn earworm

Corn leaf aphid

European corn borer (2nd gen.)

Southwestern corn borer (2nd gen.)Stalk rots

Ear / kernel rots

Nematode sampling

Soil fertility


1 This timeline is estimated for central Missouri. For the northern third of the state, advance the timeline by 2 to 3 days. For the southeastern “Bootheel,” move the time-line back by 10 days.

Timeline for Soybean Pests or Pest/Crop Management Activities for Central Missouri 1

Pest(or crop management activity)

M a y J u n e J u l y A u g u s t S e p t . O c t .

Root disease complex (root rots)

No-till winter/early-spring weeds

Early-season weed control

Nematode symptoms

Determine plant stands

Seedcorn maggot,Seedcorn beetles

Wireworms, White grubs

Grape colaspis - larvae

Cutworms (usually black)

Thrips

Bean leaf beetle adults

Green cloverworm,Mexican bean beetle, Blister beetles,Yellow woolybear, Thistle caterpillar,

Garden webwormPotato leafhopper

Check roots for cysts

Soybean cyst nematode

Assessing early-season weed control

Late postemergence weed control

Septoria brown spot, Bacterial blight,Downy mildew,

Frogeye leaf spotSoybean mosaic virus,Bean pod mottle virus

Sudden death syndrome,Brown stem rot, Charcoal rot,

Pod and stem blight,Phytophthora, Rhizoctonia

Grasshoppers

Soybean podworm

Spider mites

Stink bugs

Root knot nematode

Nematode sampling

Weed mapping and assessingoverall weed control

Soil fertility winter


Timeline for Cotton Pests or Pest/Crop Management Activities for Southeastern Missouri

P e s t (or crop management activity)

A p r i l M a y J u n e J u l y A u g u s t S e p t .

Cutworms Seedling-4" leaf

Thrips Seedling-4" leaf

Soil applied herbicides

Armyworms Seedling-4" leaf

Early post weed control 3–8" tall

Seedling diseases Seedling-4thleaf stage

Plant bugs 1st 4 weeks of squaring

Aphids Seedling-open boll

Boll weevils Seedling-open boll

Cotton bollworm and Tobacco budworm Squaring-post bloom

Spider mites Squaring-harvest

Whiteflies Bloom-harvest

Mid post weed control 8–14" tall

Wilts Bloom-1st open boll

Lay by weed control

Foliar diseases 1st open boll-defoliation

Root-knot nematode Bloom-harvest

European corn borer Bloom-harvest

Boll rots 1st open boll-harvest

Cabbage loopers Bloom-harvest

IPM1006 New 1/01/5M

■ Issued in furtherance of Cooperative Extension Work Acts of May 8 and June 30, 1914, in cooperation with the United States Department ofAgriculture. Ronald J. Turner, Director, Cooperative Extension, University of Missouri and Lincoln University, Columbia, MO 65211. ■ UniversityOutreach and Extension does not discriminate on the basis of race, color, national origin, sex, religion, age, disability or status as a Vietnamera veteran in employment or programs. ■ If you have special needs as addressed by the Americans with Disabilities Act and need this pub-lication in an alternative format, write ADA Officer, Extension and Agricultural Information, 1-98 Agriculture Building, Columbia, MO 65211, orcall (573) 882-7216. Reasonable efforts will be made to accommodate your special needs.

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