INTRODUCT I,ON

ORCHARD OPERATIONS FOR AVOCADOS AND CITRUS in Southern California

This publication is a compilation of some of the general ' recommendations for orchard practices in Southern California avocado and citrus growing areas. They are not all-inclusive, nor will they apply to all situations.

The jobs listed, however, include most of the activities occurring during a year's time. The timing of operations will vary from year to year, but it is important to be prepared for the jobs when they should be done.

Any ,one or more operations that are not done when necessary may result in a significant loss of yield, or of fruit quality. Fruit that is graded out and not suitable for fresh shipment will fast cancel the savings of otherwise efficient practices.

Irrigation, fe~tilization, and other practices are also important to the vigor of the trees and the long- term bearing capacity of the orchard. Inadequate practices ofteR show up in later seasons in • the form of dieback~ poor tree condition, tipburn, low yield, and poor fruit quality and size.

Orchards on steep slopes. with inadequate roadways and drives for fruit hauling and grove work, will be more costly and difficult to care for. Poor or untimely farming and management practice's commonly cause costs to be higher than necessary and returns to below. Orchards should be designed to minimize annual costs of care.

Weed control is one operation that can be very, , costly 1f treatments are delayed or poorly done. If weed control has been neglected or weed control on land ad­jacent to , the planted. area is inc1u,ded, costs will be much higher. Elimination of an existing weed' problem is more costly than maintenance of a normal weed control program. Delayed weed control is probably the most frequent cause of costs being higher than expected.

Acknowledgment: This . is a revision .of a publication entitled "Orchard' Operations for Citrus and Avocados in San Diego ,Co.unty" by the same authors. R.G. Platt, Extension Subtropical Horticulturist and R.L. Branson, Extension Soils and Water Specialist assisted in providing data and in review.

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CHECKLIST OF ORCHARD OPERATIONS

Irrigation:

Fertilization:

Micronutrients:

Replanting:

Diseases:

Rodents:

Weed Control: .

Frost Protection:

Orchard Thinning Avocados:

Topworking:

Pruning:

Harvest:

Equipment:

Material Orders:

Record Keeping:

Determine when and how often. Determine amount to be a.pplied;·

Use leaf analysis on mature trees. Determine materials and amounts to use.

Treat with used.

specifically if other treatm.ents

symptoms become general. Combine if regular maintenance sprays are

Evaluate and rate trees. Remove and fumigate if necessary. Order trees. early. Plant during •. s:pring if possible. Buy disease-free trees.

Avoid spreading avocado root rot. Check citrus for gummosis. Spray skirts and paint trunks as necessary with

. Bordeaux. Take preventive steps against infections.

Check often and regularly for gophers. Use traps or poison. Prevent rabbit damage to young trees.

Use correct chemicals as recommended. if weeds are too large. Do the job large.

Mow before spraying before it gets too

Check equipment early. Test thermometers. Watch temper­atures closely on cold nights. Refill heaters and storage tanks promptly. Wrap the trunks of young trees.

Record yields of avocado trees. Map and plan tree removal scheme. Follow a progressive system.

Follow up work of pruning, suckering, selecting, tying, and supporting of new grafts. Prevent pest buildup and frost damage to new grafts.

Keep branches from interfering with water pattern. Use as a slack season job. Prune lemons as necessary. If time permits, remove interior deadwood, especially on avocados •

. Pick avocados at proper maturity. Be sure drive rows are in good condition.

Maintain equipment properly to prevent breakdowns at crit­ical times~ Do annual maintenance and safety training during slack periods.

Early ordering of new trees, fertilizer, herbici'des, heater fuel, and pest control jobs is essential to a well-managed enterprise.

Record weather, irrigations, water use, labor, expenses, etc. Use records to plan operations and schedule jobs.

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Safety:

IRRIGATION

Remove fire hazards. Prevent excessive grass and weeds around buildings, trees, and improvements. Maintain,proper and required guards on equipment. Post safety and legal notices. Provide secure chemic,al storage. Maintain ade­quate health and safety equipment. Provide required safety training.

Prevent the root zone from becoming too dry. Check deeper soil, especially in late summer, fall and dry winters (water use in winter is low but continues-­light, shallow rains are misleading). On shallow soils don't restrict root growth by too limited water distr.1bution, and don't over-irrigate above hardpans. Where small areas of soil are wet, or irrigation must be shallow, short, frequent irrigation is necessary since there is little soil moisture ,reserve.

On heavy soils avoid wetting- the trunk area of citrus to prevent rotting of large roots and the buried portion of the trunk. Excess moisture also will cause the feeder roots to rot, and the tree will wilt or die.

Dry soils tend to result in tipburn, sunburn, and dieback the following season, especially when mite, scale, heat, and wind damage occur too. Dryness also reduces fruit growth and increases fruit drop. Avocados can be permanently dam­aged by sunburn when the soil is too dry. Your avocado trees need special atten­tion until the trunk and larger limbs are protected by foliage.

Trees need about 3 acre feet (about 980,000 gallons per acre) per year,:including rain--trees with perennial grass cover crop need about twice as much for adequate growth. Drip irrigation will save water, particularly with young trees. The saving may range from 25-50%. Determine timing by using tensiometers (12- and 24-inch instruments, with results plotted on a graph), a shovel, a soil tube, and constant observations. Leaf burn or tipburn from salt excess is uaually a sign of inadequate irrigation, too much salt in the water, or both. Apply extra water periodically when irrigating avocados with sprinklers to leach salts to lower levels and prevent buildup in root zone.

Normal irrigation intervals vary depending on soil type and irrigation method. Citrus planted on soils holding more moisture can be irrigated at less frequent intervals than avocados. Where alternate middle irrigation is used, longer intervals can be used before irrigating the same soil again.

The avocado cannot tolerate drought. Excessive moisture is also bad because it -restricts root activity and favors root diseases.

The soil serves as a ~isture reservoir. Water is stored in the spaces sur­rounding soil particles. Clay soils store more water per unit of volume than sandy soils. Weather conditions and amount of leaf surface determine how fast your trees use water. Two factors thus determine irrigation needs: How much water the soil holds and how much water is being used. It is just as important to know when to turn the water off as when to turn it on.

Drip Irrigation

Most new orchard plantings are now using drip or other low-volume irrigation systems. Some mature groves are being converted. Drip irrigation is the fre­quent, slow application of water to soil through emitters that are located at

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selected points along water lines or on short branc.h tubing at each tree. The volume of soil wetted by drip irrigation usually is much less than that wetted by other irrigation methods. It may be only 10 percent of the soil area for newly planted. crops. Obsenrations show that at least one-third of the soil in the root zone under ' mature crops should be irrigated, and that crop performanc.e improves as the amount: wetted increases to 60 perc.ent or more. The amolJnt of 80il w'etted depends on soil characteristics, irrigation running time, and the number of emit­ters used. This number ranges from one emitter p~r tree for new plantings to eight or more emitters placed in line or around large trees. The use of at least two emitters will reduce the chance of tree damage due to failure or plugging.

There are several advantages to drip irrigation. Drip i:r'rigation can reduce operating costs, and this has been the main interest in this new met.hod. Drip systems can irrigate with significantly less water than is required by other more common irrigation methods. Young orchards irrigated by a drip system may require only one-half as much water as those under sprinkler. As orchards mature, water savings from a drip system diminish but still may be important because of the scarcity and high cost of water and power. Much of the water savtng on mature trees will be water otherwise wasted such as from runoff and evaporation. Be sure to anticipate that water use and system capacit.y requirements will be greater f6r older trees than at the tim.e of planting, and design the system with adequate capacity. Forty to sixty gallons per tree per day may: be required during peak use in late sutillller. Because much of the soil surface never is wetted by irrigation water, weed growth can be reduced by drip irriga.tion. This lowers costs for weed control.

Fertilizers can be injected into drip irrigation water to avoid the labor needed for ground application. Sevex'al highly soluble materials can be used for this purpose, and new products that widen the choice are being introduced. Greater control over fertilizer placement and timing through drip frrigation may lead to improved fertilization efficiencies. Rates of application are given below.

There are also problems in drip irrigation; they most often involve clogging, inadequate irrigation, poor uniformity of water delivery, salt accumulation, and runoff. Careful checking to insure that trees are recelving adequate water is essential, particularly with avocados.

Sprinkler Irrigation

Various plans may be followed for sprinklers. Some growers will start with a basin, change to a spitter sprinkler, and then to a revolving sprinkler. Others start with a ' spitter, with a later change to the revolvin.g sprinkler. In some cases, revolving sprinklers have been used from the very beginning, particularly where water costs have not been high.

Dec.isions must be made sprinklers permanently risers.

between permanent installed on short

sprinklers, portable sprinklers, or m.oveable hoses attached to permanent

The prinCiple to remembe.r is that the water pattern should accura.tely cover the root zone away from the trunk, and that water should not be applied at too fast a rate. A common cause of runoff from irrigation water is spr:tnklers applying water faster than the soil can absorb it. This is particularly true on clay soils or on well drained soils with clay or compacted subsoil layers.

In planning an irrigation system, a decision must be made regarding t.he balance

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between the initial cost and operaUng or labor cost. Permanent sprinkler and drip systems are c.onvenient and. reduce labor needed in many case;;. However, on older systems and on larger orchards portable sprinklers have been efficient and satisfactory since labor is ::Lnvolved in checklng sprinklers E']ell when they are permanently installed. \l1ith present trends i.n la.bor costs and costs of equip­ment, most syste·ms are. permanent.

Both sprinkler and drip irrigation must be done with care. It is ·easy to give too much water, especially when the sprinkler . or emitter wets the trunk or is near the tree. This can cause waterlogging, root rot, aud gummosis. Eventual tree failure in both citrus and avocados can result. It will be helpful to plan that eventuaLly the sprinklers will cover all of the. soil that is not immediately under the trees. Sprinklers should be on short risers and as low as poss:i.ble, since Colorado River water and local water with high salt content will cause leaf drop from chloride and sodium depo t:dted on citrus leaves i.n inland areas where evaporation is rapid. In shallow soils it i.8 important to use as much aoi1 area as pOSSible, thus getting a maximum volume of water available to the tree. Ten­siometers are helpful in deter.mining the irrigation program. Where maximum BaH wetting does not occur t as with drip, irrigation wi.11 be more frequent.

Furrow irrigation is effective under proper conditions, but most hillside loca­tions can be more effect.ive.ly irrigate.d with sprinklers or drip. Furrow irri­gation is now ·.r:arely used in new pla.ntings but is common in old orchards.

FERT 11 IZATION

Nitrogen

On young trees, give adequate nitrogen for. vigorous growth but not enough to burn the roots. Distribute the material evenly on the soil above the root system jU8t before irrigating or before rain is expected. Following are approximate rates per tree using ammonium nitrate as an example. For fertilizers other than ammonium nit:r:ate adjust the amount of material applied according to the percent of nitrogen.

Avocados:

1st year

2nd year

3rd year

4th year

5th year and older

Citrus:

1st year

1 level tablespoon per month for 8 months (1/10 lb. N/yr.)

1/4 cup every other month (1/5 lb. N/yr..)

1/2 lb. in Feb., and 1/2 lb. in July (1/6 lb. N each application)

l~ lb. in Jan. or Feb. 0/2 lb. N)

3 to 6 lb. in Jan. or Feb. (1 to 2 lb. N)

Vary according to leaf analYSis

1 tablespoon of ammonium nitrate 3 or 4 times

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2nd year

3rd year

4th year

5th year

6th year

1/4 lb. nitroge.n each yea.r, in split applications, Fcb. and July.

1/2 Ib' • nitrogen each year, in split applications, Feb. and July.

3/4 lb. nitrogen each year, in split applications, Feb. and July.

1 lb. nitrogen each year, in single or split applications.

Amount indicated by leaf analysis.

For producing trees, major nutrients should be maintained at the following levels in the leaves.

Avocados:

Lemons:

Oranges:

Grapefruit:

Maintain 1.6 - 2 . 0% nitrogen in August-October leaf samples for Fuerte and Zutano. Leaf nitrogen for Hass arid Bacon should be about 2.0% and Hass will probably need more fertilizer than Fuertes to obtain the desired level.

2.25 - 2'.5% nitrogen in leaves from mature spring flush sampled in August-October period.

2.4 - 2.6% nitrogen in an August-October 'leaf sample. Increase or decrease nitrogen as indicated. Apply Jan­uary or February.

2.0 - 2.2% nitrogen in an August-October leaf sample. Apply January or February.

Apply fertilizer in the early spring (February) so nitrogen will be in the trees before bloom and fruit set on mature avocado and citrus trees. Another appli­cation for avocados may be made in July. For better orange fruit quality, apply all nitrogen in February. Young citrus .from the second through the fourth year should have the fertilizer divided :i.uto three or four applications during the season. Phosphorus and potassium should be applied when a deficiency is indi­cated by leaf analysis.

Remember that in fertilizing young, growing trees it is important to maintain a high level 'of . nitrogen for tree growth. It is when the trees mature and crop production becomes established that excesses should be avoided and fruit quality considerations become more important.

Also in cases where trees have been neglected or have become deficient, fertilization may be necessary at other times to renew tree vigor, even in the fall.

Phosphorous: Most citrus soils in California provide sufficient phosphate. Rare cases of deficiency, mostly in San Diego County, have resulted in fruit quality problems. Correction has been best using 10-25 pounds of treble super phosphate banded on the 60i1 around each tree. Due to rapid 90il fixation ml~{ed fertili­zers provide little if any correction. They are sometimes used on a maintenance basis however.

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Potassium: Def:tciency of potassium is also uncommon. Lemons have shown a. quality improvement in some cases" Thirty pounds of potassium nUrate per 100 gallons (If water sprayed ~vhen leaves are two-thirds expanded can be used" Ten to 25 pounds per tree applied to the soil will also provide benefi/t.

Netther phosphorus nor potassium deficiencies have been recognized in California avocado orchards eve.n in aI'eas where cit'rus has benefitted from treatment.

MICRONUTRIENT'S

Avocados:

Zinc may be sprayed on trees anytime, but spring i~ best when spring-cycle leaves are expanded. Use 1 lb, zinc sulfate (36% metallic zinc) :tn 100 gallons of water or 2 Ibs, zinc oxide in 100 g8.110118 of "Tate.r. Soil appIie.ation of :z:inc can be made anytime during the year. This treatment should last abou.t five yea!".;;, Place zinc sulfate1.n two--foot . bands around the trees at the drip line. Soil applications are. only effective in neutral to acid soils.

The following amounts of zinc sulfate contairdng 36% metallic zinc may be used for soil application:

2 5 7

10 15 20

Pound.s per tree

0.7 2.0 2.6 3.3 5.2 6.5

Aerial application of z:f.nc has sometimes been effective. Six to eight pounds of 36% zinc sulfate in 20 gu110ns of water per acre is suggested. The concentration should provide the same amount of zinc per acre as conventional spray methodR.

Citrus:

Zinc., manganese. copper, and iron may become defic.ient. Spray zinc and manganese when the new growth is near full expansion for best results. More than one spray annually may be needed. esped.ally if treatment is combined with pest control spray. One formula that can be used by ltself for correction of a deficiency is 1 lb. of 36% zinc sulfate plus 1 lb, of 28% manganese sulfate per 100 gallons of w8,ter.

Copper and iron deficiencies B.re not generally problems :1.n Southern Ca11.fornia orchards. Copper deficien.cy occasionally occurs, however, reducing frli1t quality. Copper Bordeaux sprays normally ca.n correct the problem. Iron defi­ciency is rare and usually on high lime content soils. Careful irrigation and occasionally iron chelate m.ay correct. the symptoms.

Fertilization Through Drip Syste~~

The experiences of growers in applying fertili.zer materials through drip irri­gatlo1.1 systems have varied. In general, this method of applying fert:i.1izers has been found to be eonvenient and 8atisfactory~ but there have been some problems .

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This is to give some guidelines which can help you avoid snch problems and wh:f.ch can also help ensure that drip irrigated trees a.re adequately fertilized. These guidelines are int.ended to be flexible because drip irrigation is relat:f.vely ne,,! and there is a good deal to be learned about fertilizing with it. We can expect that there ~;ri1.l be refinements made. in how to do it as time goes by.

For nitl:ogen application, urea, ammonium nitrate, ammonium sulfate, and calcium nitrat.e may be used. These materials are all highly soluble--a prime requirement of any fertilizer that is to be distributed through a drip irrigation system.

From a nutrient standpoint, you can get similar results from the use of any of these fertilizer materials, pound for pound of nitrogen. Differe.nces among them in chemical characteristi~s, however, should be taken into account in management. Most of these nitrogen fertilizers release ammoniulll and this in turn produces residual acidity upon reactiotl in soils. The residual acid:f.ty of urea J ammonium nitrate, and ammoni.um sulfate amounts to 158, 185, and 550 lha., respecti~ely per 100 pounds of material. These figures represent the quantity of lime that would be required to neutralize the acidity produced from an appli.c.ation of 100 Ibs. of material in each of three forms. Note tha.t ammonium sulfate produces consider­ably more residual acidity than the others. Because of this, .it is less suitable for use on soils th,st are already naturally acid because of the possibility of causing excess soi.). acidit)' (pH belo,"T about 5.0 for most crops). Naturally-add soils are common in San Diego and Santa Barbara County avoc.ado and citrus areas. The water itself .is a s.ouree of some c,alcium, ho·wever, in most cases.

Nitrogen fertilizers with lower reBidual acidity than ammonium sulfate may also acidify soils that do not contain lime. A downtrend in pH may require switching to calcium nitrate, which being residually basic~ can reverse such a 'trend.

When fertilizer is distributed through drip irrigation systems t the material is applied in localized zones. As a result, the potential for acid:i.fication is somewhat greater than when the material is broadcast. A check on soil pH in the rootzone from time to time may be desirable when residually acid fertilizers are applied through drip systems on soils that are already naturally acid. About once every two years should be adequate.

Nitrogen fertilization rates for citrus and avocado trees must take into account the tree ~ge. During the first year after planting, about 1/10 of ' a potUld of nitrogen per tree is applied. This increases progressively as the trees mature to about a pound or it pound and a half for most varieties. S:i.nce drip irrigation involve.s frequent fertilization» a chart has been developed for nitrogen fertili­zers that gives the amount of mater:f.al that should be <:i.pplted per tree per month according to age.

1st yE~ar 2nd year 3rd year 4th year 5th year and older

Pounds Nitr.ogen Fertilizer l)er Tree Per Mon.th

Urea

0.03 .06 .09. .14 .28

AmmonIum Nitrate

0.04 .08 .13 .19 .38

Calcium Nitr~

0.09 .17 .29 .43 .90

This table is based on the assumption that nitrogen is applied monthly for , an 8-month irrigation period; the total nitrogen applied during the 8-month peri.od

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increases from 0.1 lb./tree (one year old) to 1 lb,/tree (5 years an~ older), To illustrate its use, assume you have an orchard of 2,000 trees that are 3 yeasrs old and urea is the nitrogen source. According to the table, the .monthly re­quirement per tree 1.8 0.09 lb , of urea which, when multiplied / by 2,000, amounts to 180 lbs. of urea required per month for the orchard. Amounts of some other nitrogen fertilizers that will supply an equalamOl.lllt of nitrogen are also shown in the table.

Timlng of nitrogen fertilization is another important consideration~ particularly for producing d.trus. The nitrogen requirement of the producing trees is greatest during the period of flowering and fru:l.t setting. Mature Valenci.a trees, foT. example, should not be fertilized with nitrogen during the period from about May through fruit harvest because of possible adverse effects on quality. There :l.S some evidence that avoidance of nitrogen fertilization during this period is desirable for mat.ure navel orange and grapefruit trees as well. According to this information, we have about five months, December through April, to fertilize such crops. It ma.y turn out to be necessary to fertilize even during some rainy weather or to broadcast fertilizer in ord.er to apply the required amount of nitrogen when using drip systems.

In the case of young, non-bearing citrus, the period of nitrogen fertilization is not critical. Applications are best during spring and summer since fall appli­cation may increase susceptibility to frost. The same appears to be true for avocado trees,' The time of blossoming of mature avocados. however, may be a period during which you should not fertilize with nitrogen, This has not yet been definitely established.

Nutrients other than nit'rogen that may be needed in a fertilization program for citrus and avocados here in Southern C..alifornia all have one thing i.n common-­unlike nitrate, that they do not move down through solI readily. This presents some problems in fertilizing with them. Zinc, for example, in the commonly used form, zinc sulfate, moves very slo~l1y through the soils. It is more efficient to apply it to the foliage. A very small amount of zinc is required for it is ab­sorbed readily through the leaves, but there may be situations where it is not convenient to apply zinc in this manner. Avocado trees may be on steep hillsides or of such size that getting spray equipment into the orchard :f.s a pr.oblem. A guideline for fertilization wi,th zinc sulfate through a drip system is shown below:

Zinc Sulfate Per Tree Per Month

Tree age - yea~

2 5 7

10

Pounds 36% Zinc Sulfate

.33

.67 1. 33 2.00

The other elements that should be mentioned again with drip irrigation are potas­sium and phosphorus.

There is no documented case of phosphorus or potassium defl.ciency on avocados in Southern California. Whe-re potassium deficiency occurs on citrus, it mny be corrected with a foliage spray or soil application of potassium, Correction by soil application takes longer but on the other hand costs less and provides a longer lasting reserve. If potassium Is n.eeded, it is advisable to spray the

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trees for quick response and also make a soil application to raise the Goi1 potassium level to meet the long tem needs of the crop. A guide'line rate of potassium fertilization for citrus by drip irrigation is as follows:

P(jtassium Sulfate Per 'l'ree Per Year

Tree age - ye~r~ Pounds Potassium Sulfate

up to 5 over 5

2.5 to 5 .5 to J.O

Potassium fertilization should not be overdone because excessive soil appli­cations can cause a salinity prpblem.

Fortunately~ phosphorus deficiency is of rare occurrence on tree crops since it is diffic.ult to c.orrect. Application of phosphorus through a drip irri.gation system is not recommended with high calci\.lIll water, The reason 1.6 that phosphorus reacts with the. cald.um in i.rrigation water, forming a. white precipitate of calcium phosphate that can clog f:i.lters. Where problems have developed wtth drip irrigation fertilization, they have been almost entirely associated wi.th phos­phort~s. In fertiliztng citrus with phosphorus, it is advisable not to apply it through the drip irrigation system, at least at this point in techn?logy of ~rip irrigation. It is safer to put the phosphorus on the soil under the emitters. In time, the phosphorus will mOVE: down into the rootzone.

Fertilization through drip irrigation systems represents a new process and there is much to be learned about it. There is some evidence that applications of slow moving plant. nutrients such as zinc and phosphorus are more effective under drip irrigation .than with convention.al irrigation methods because of feeder-root development close to the surface beneath emitters, and also because the nutrients can be expected to move deeper under drip irrigation than when applied wit.h sprinkle.r or furrow irrigation. Also, there are indications that nitrogen fertilization under drip irrigation, involving sruall increments and fre~uent applications, may be more efficient and require som~what less nitrogen per year than is usually applied. In the period ahead, leaf ana.lysis should be extremely valuable. in helping to refine pJ:esent .fertilization gu.idelines and thereby develop the best fertilization programs with drip j.rrigl!Ltion.

PEST CONTROL

Pest c.ontrol requil:ement.s vary from area to area. sites and .predators 15 increasingly available. RECOMMENDED FOR AVOCADOS EXCEPT IN OCCASIONAL CASES

Btological control by par.a­NO PEST CONTROL SPRAYS ARE Olr SEVERE INFESTATION', Avo--

cado brown mite is serious in some years. but biological control does occur and damage has been less ~he!'e no treatment is given. Omnivorous loopers and aruorbia moth occasionally cause leaf a.nd fruit damage,' but biological control is the best con.trol.

Biological control of several. citrun pests is effective. Tctal control can better be c.alled "j.ntegrated pest nlr'.magement." Complete dependence on biological control does not always maintain an adequate level of control because fruit and tree damage will be excessive, and some pest:3 have no adequate predators. On the other hand, complete ~hemical control can result in elimination of beneficial insects. Also if there are no pests at all as hosts, beneficial insects may disappear.

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The 8olution~ then, for effective~ integrated pest management is t:o use. peati'­cldes only when lteceSSa'l."y and only those that result in minimum damage to bene­f:i.cial insects. Spot spraying may be used to eliminate localized pest buildups w:i.th minimum kUling of beneficial insects. Stay OJ) top of the pest situation. 80 fruit damage. will not result in excessive grade.out. Parasites and predat.ors can. sometimes be utilized with selected pesticides to provide for integrated con­trol.

Elimination of ants is the most effective way to encourage biological control of harmful insects. Ant control is most effective when the entire property is treated. Effectiveness of full cove.rage can be prolonged by spot treatment and border treatment. Apply ant control materials as needed--ants are most active in warmer weather (spring). Watch ,·for buildup every month.

MAJOR PESTS

Avocados:

Citrus:

Pest

Snails Brown mite Looper amorbia Rats Greenhouse thrips

Bud mite Rust, or silver mite Red spider Scale Thrips Aphids Orange worm Snails

Major Da.mage

Foliage, blossom, fruit damage Leaf, fruit damage Leaf, fru:l. t damage Fruit loss Leaf, fruit damage

Crop reduction, grade loss Grade loss Weakens tree, leaf drop, dieback Weakens tree, leaf drop, dieback Fruit scarring, retards growth Retards growth Fruit drop, grade loss Fruit damage, foliage loss

The "Treatment Guide for California Citrus Crops" is available for pest control recommendations. See the local Agricultural Inspector for legal regulations and recommendations applicable to each district. Occasionally, special use permits are approved for severe problems. Most citrus growers utilize the services of licensed pest control advisors and pest control applicators.

Watch for pest damage and buildup every month so that prompt treatment can be applied when necessary.

THINNING AND TOPWORKING AVOCADOS

Avocado trees planted at 20 x 20 foot distances will normally be,gin to crowd at about 12 to 15 years of age. The resulting shading of lower branches causes a drop in production and makes picki.ng from high branches difficult and expensive. Thinning is necessary to permit more light to reach the lower branches. Total yield will increase from the fewer trees remaining.

Design a pattern for tree removal before trees crowd and lower branches are. shaded out. Trees can be trimmed back or topworked to a better variety. Thin­ning can be done a,fter the, crop is harvested.

Topwork low producers and. odd varieties to standard varieties. In some cases a cross-pollinator for the Fuerte avocado can be grafted to the stump of a removed

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tree. CroBs-pollinator varieties such as Topa Topa, Zutano, and ·Covacado h;nre increased Fuerte ')'ields. Provide careful follow up to make a good t:ree and p!:'~­vent breakage and sunburn.

REPLANTING

In replanting an orchard the most efficient method is replacement of total blocks of low producing trees. Individual replanting can be successful. with proper care. Poor trees end empty spaces should not be tolerated unless the grove has a short commercial future (five years or less). Plant as soon as frost danger has passed (March-Apl:il-May) but before! the weather is too hot. Competition from bermudagruss will prev~mt proper grow,th of young trees. 1ft7e.ekly water and care is n~cessary. Be SUt'€ the bal:), of sot1 whi.ch contains m08t of the roots is thoroughly wet at each :f.rrigation. (s()1!letimes the l\-'ater surr.ounds the ball but does not penetrate). Also, be sure the surrounding soil does not remain too wet. Sprinklers may cover some areas not dried by root: aetion. A connnon problem with citnls replants is too much water.

Fertilize regularly but lightly. Soil fumigation will be helpful for establish­ing citrus replants. Several fumigants are available, and rates vary depending on whether nematodes or fungi are to be controU.ed. Nematodes a.re not a problem with avocados, but some ben.efit Dlay result from eliminating competition from weeds and neighboring trees.

Orchard charting each year will help determine trees or blocks of t~ee8 that should be replaced. Mark the trees to be removed after the crop is picked.

Trunks of replants ~hould be wrapped for protection against sunburn, weed oil, physical damage and frost. Many trees have been lost unnecessarily from frost when trunks were left unprotected.

DISEASE CONTRQ&

Avocados:

Disease

Root Rot

Sunblotch

Cankers

Verticillium Wilt

Control . -Buy dlaease·~free trees and resistant rootstocks if ava:Uable. Do not plant in clay or poorly drained so~18. Irrigate poor soils carefully. Dry out known infected areas where trees have been removed. Prevent spread of .infection, isolate diseased areas, est.ablish chemical barriers, sterilize tools~ remove diseased trees. Do everything possible to prevent moving ''let soil to clean areas.

Remove and replant.

Cut out infected bark and wood and paint with Bordeaux.

Do not remove dead-appearing branches until a new flush of growth has appeared. Prune dead branches. Eliminate nearby susceptible plants, such as tomatoes, squash, etc.

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Sunburn

Citrus:

Adequate, timely irrigation. Shade young t,reeI3, and use whitewash on exposed litllbs and trunk after extensive damage, pruning. or topworking.

Buy disease-free trees. Keep down sources of infection. Avoid conditions which contribute to infection. Cover ' susceptible parts of trees with , fungicides or disinfectants to prevent ent.rance of organisms,. Use resistant rootstocks.

Disease

Fruit Rots

Brown rot on navels and lemons

Internal breakdown Stylar end rot

Rind rot

Brown rot, foot rot, dry rot

Scaly Bark

Virus diseases

GOPHER CONTROL

Control

Clean and careful fruit handling.

Bordeaux spray on lm"er portion of tree before first rain. May need to repeat in wet years.

Avoid moisture stress and overmaturity.

Prevent physical damage to fruit.

Obtain clean trees, plant high, use planting and before winter; do not prevent wet conditions near trunk. fections. Examine once a year.

Bordeaux when overwater and

Cut away in-

Remove when nonproductive. Prune in early stages.

Buy trees certified to be disease-free.

Strict control is necessary to prevent root and trunk girdling and death of trees, especially c.itrus. Runways interfere with movement of irrigation water.

A mechanical gopher bait applicator has been developed for treating heavy infes­tations. Use it in early spring or in the fall while the soil is moist enough to make good burrows and while gophers are active.

For hand control, use poison.ed bait placed in the main rUnl..rays with a probe. Follow up with gophe,r traps on hard-to-kill gophers. Destroy mounds so new workings will be n.oticed. Spring and fall, after rains, are the best times.

For rodent control, obtain bait from the Agricultural Commissioner to poison go­phers, rabbits, squfrrels, field mice, etc •. Continuous checking and prompt con­trol are important.

WEED CONTROL

Mowing - Mow often enough to prevent weed growth from interfering with sprinklers, picking, gopher control, and other practices. Mowed grass continues to use water and compete for fertilizer nutrients. Perennial grasses such as bermuda are very competitive and damaging to citrus and young avocados and may prevent a good start.

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Contact Herbicides - Spray when weed growth reaches seedling (2-3") size. Spray bermudagrass at 20% regrowth. Let it use reserve food in roots, but don't ll':!t it start replenishing r.eserves. This may be every two to three weeks during summer.

Soil Active Herbiddes - These kill annual seedlings and some also kill estab": lished growth. Uniformly spray the ground wHh recommended dosages. Use enough wa~er for coverage (50-100 gallons). Apply in spring and tall so that rainfall will leach the material into the soil. Several materials are registered for use. Follow the University of California recommendations and the directions on th~ label.

FROST PROTECTION

The Fruit Frost Service season is November 15 to February 15. Predictions and warnings are provided nightly by radio. Heaters, oil, and wind machines should be in readiness by November 1 until April I to take care of early or late frosts. Test thermometers before November 1 at announced locations. Test wind machines when possible on a cold night when air is heaviest to be sure they will not become overloaded under use on cold nights. When damage occurs, work with your packer to evaluate fruit damage and. picking .schedules.

PRUNING

Avocados:

The primary need 1s to remove lower branches where sprinklers are used so water will be evenly distributed and fruit receives miniroum damage. Prune after the fruit is harvested. Rp~ove deadwood. Skirt pruning . can also assist in control of snails and ants.

Lemons:

Mechanical topping and hedging can be dene to keep trees to a manageable size and to help maintain vigor and production. Some hand pruning will be necessary occasionally to remove lar-ge stubs and weak branches.

Oranges:

Very little pruning is necessary. Some deadwood removal will be helpful to pre­vent fruit damage, facilitate picking, and to prevent picker injury.

For young trees, very and occasional crossed later breakage.

little pruning :f.s needed. Remove suckers from the trunk branches to provide for good tree structure and minimize

RECOGNIZING PROBLEMS

The operator of an orchard has to pay special attention to problems that will cause damage to the fruit. Insect damage and wind scar arc examples. Workers must avoid practices which will damage fruit, such as use of too much chemical in sprays, herbicide sprayed on the fruit or drifting in the wind and damaging fruit by eq ipment. Fruit that is damaged will be graded out and earns less money than picking and hauling costs.

When problems arise in caring for trees, you have to caused the trouble, then apply your knowledge to change tural or management procedures'.

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try to decide what has things and improve cul--

Various types of problems are common in growing citrus. Some can· be recognized by symptoms of leaf color, leaf patten), or growth habits. Others' are not read­ily apparent, and symptoms may be hidden until the tree is badly damaged or be­yond help.

Yellow trees, or yellow foliage color, is a common symptom and can indicate several problems. Over-irrigation is one of the most common problems. Trees become yellow from too much water, mainly due to 'lack of oxygen. Trees on Troyer citrange rootstock are more sensitive . to overwatering than most others, especially when young. Dry trees will also appear yellow, but are usually wilted.

Nitrogen deficiency trees are neglected. smaller root systems growing season.

will resul.t . in yellow leaves and is not too common unless Nitrogen most often is deficient in young trees that have

and, therefore, need more frequent applications during the

Damage to the root system from gophers, fertilizer burn, -tools, chemicals, etc., cause yellowing. This is often most severe on one side of the tree, or even on single branches that are supported by a root on the same side of the tree.

Foot rot, or rot of the larger roots from excess water near the trunk, commonly results in weak trees. The damage is usually below ground. Yellowing may be noticed first in the top of the tree. This, too, may show more on one side of the tree, reflecting root damage to t·he same side. Both avocados and citrus can fail due to waterlogged soil. Trees will suddenly turn yellow or brown. Excess moisture can cause rotting of the roots and tree death with no disease present. Sudden collapse may occur after stress, such as frost or a hot day.

The trunk area of the tree should be checked annually. Damage to the root system by rot cannot be repaired, but increase in the damaged area may be stopped if the roots are exposed to drying.

Twig dieback and leaf drop occur when leaves lose water faster than the tree can replace it. Leaf scorch symptoms may appear immediately or drying and dropping may occur several months later. The damage can occur during periods of heat, low humidity, and winds, even while trees are well irrigated. Good irrigation will minimize the damage, but not always eliminate or prevent it.

Diseases result in various symptoms. Some, however, such as viruses may have few if any visible symptoms. Often a vague stunting, reduced growth, or distorted leaves are the only symptoms. Virus diseases cannot be eliminated from a treets system, so careful selection of reliable trees and bud sources. is necessary.

Avocado trees are extremely susceptible to damage from sunburn when ne\o7ly planted and when leaves do not shade the trunk and larger brall.ches. This can cause permanent stunting. Shade the trunk or use whitewash and be sure irrigation is adequate.

Fungus diseases of the tree infect the soil and attack the roots, trunk, foliage or fruit. Prevention can be practiced, and infections may be cured. However, if extensive damage to large roots occurs, trees will probably have to be replaced.

Nutrient deficiencies result in various changes in color and leaf patterns. Sometimes various deficiency symptoms occur simply as a result of poor care, such as inadequate watering and weed control. Weak, old trees often show deficiency

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symptoms. symptoms.

Better care sometimes results in ne.w growth without de.ficiency

Poor growth often r.esults where extensive, permanent cover crops are maintained. Bermudagrass competition weakens citrus trees considerabl~, and young trees will rarely gro;.] satisfactorily in grassy soils. In addition, grass hides ' gopher mounds, broken sprinkler pipes, and is a fire hazard. Loss of t.rees from fire damage is common where fire reaches a grove with uncontrolled weed, growth. Weed free orchards or closely mowed cover crops often prevent or reduce fire damage.

If you see an.ything unl.lsual or wrong with equipment, find ,out why and how to corr.ect it. Get help if necessary. Costs of repaidng machinery and equipment can be much higher if malntenance is poor. Irrigatton system leaks can damage and kill trees, and waste a lot of water. Fix them as soon as possible.

It's the little thin~ that count in making a £ood grove. Good farming is an art as well as a science.

Scarring of fruit is especially bad when winds occur during rain or when the fruit is wet. Insects, especially thrips and rust (or silver) mite cause damage that prevents sale of fresh fruit.

Chemicals such as weed spray on the fruit, or tree sprays that are incorrectly used, can · cause scarring and discoloration that ruins fruit. Combinations of insecticides and nitritional sprays have caused serious losses. Spotting of the leaves can also be caused by improper sprays. Do not use combinations of mate­rials . unless you know they are safe. FolIo'", the recommendations. Even ifrec­olnmended materials are used, damage to fruit or foliage can result from too much material. If you use Y0l,lr sprayer for. one purpose, espe.ci.ally weed control, be sure it is well cleaned out before spraying something else on the trees.

With some ·problems and diseases, several things can be factors ffild frequently no one thing can be i.dentified as the cause of the trouble. An example is'gummosis, which is a disease, but a problem often directly related to irrigation pro­cedures.

Root rot is the maj or problem affecting avocado trees. \:;"hen first suspected from weak, thin foliage. tests can be made to 'confirm the presence of the fungus and steps should then be taken to prevent or restrict its spread.

Excessive tipburn usually indicates irrigation and salinity problems. irrigation is timely and adequate.

Be sure

Low production and erratic bearing is inherent in the Fuerte. If yields are less than. normal, more attention to standard orchard practices may give improvement, or as a last resort, topwork the orchard to another variety.

Rotting of the bark on the trunk just below the soil lin.e has been a problem on young avocado trees. Be, sure that sprinklers or drip emitters are not located in a way to keep the trunk wet. Wraps should be periodically inspected to prevent hidden insect damage to the trUnk and to prevent retention of moisture if the wrap is partially buried. Wraps should be removed when no longer necessary. Trees planted on hillsides should be checked to see that the trunk and bud union do not remain buried after winter soil erosion.

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MANAGEMENT AND ACCOUNTING

An adequate set of financial, personnel, and supplementary records for the farm business is basic to any commercial farming enterprise. A main purpose of all farm records and accounts is to compute the 'profit of the. far~ business each year for income tax reporting and for management decisi.ons. Labor management a.nd personnel records are increasingly important for legal and insurance purposes.

TOOLS OF MANAGEMENT .-:....-...... .

Records and accounts are diagnostic tools of management and are useful to the grower in three ways: As indicators of business success; as service tools in operating the business and providing needed information; and as instruments for locating weak points.

An annual statement of income, expense. and profit or loss for the farm. business as a whole should be developed. Also needed are occasional financial or net worth statemen,ts showing the ec.onomic condition of the business •

. Accurate records have a variety of uses in matters such as:

1. Prepar.9.tion of the income tax farm schedule and personal returns. Z. Repol'ting ls.bor costs fot' compensation. insurance. 3. Figuring social security taxes on employee,s, and reporting and remit ting

such taxes. 4. Looking up m~scellaneous information to aid in determining causes of

problems. 5. Dividing income~ costs, and profit in joint operations. 6. Obtaining gasoline tax refunds. 7. Obtaining credit.

Efficient management calls for many additional records. Some of these are as follows:

RECORD KEEPING

Daily

Weekly

Fall

End of Year

Make notes daily on jobs done, weather, rainfall, personnel actions, etc. Keep time and job recorda.

Chart tensiometer readings which should be made at least three times bet~~een :i.rrigations. Sutntnari~e labor and job records.

Summari1.e records on picking dates, yields, packout . (size~ grade)~ etc. Plan changes in orchard practices that will improve yield and packout next year.

Summarize reports on orchard practices, weather, coats, labor, equipment, and materials,

Orchard inventory -- chart the grove for needed tree removals, replants, thinning, topworking, pipe re­pairs, etc.

Compute the financial summary to determine your p;:o­fit or loss on orchard operations, your time, and

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Start of Year

your investment. ..

Adjust and make plans for the new year--improvements to be added, changes in practice¥. Order tustom work and supplies ea.rly--before they are needed and be­fore suppliers are too busy, This includes replace­ment trees, pest control work. fertilizers, wind machines. and pipe.

Order trees for two years ahead to insure delivery of exactly what you· want when you want it.

Various legal requirements conc·erning the use of labor are being implemented that have not been as significant in the past. Following is a list of items that may help you comply with regulations that apply to agricultural personnel. It is divided into three parts: The forms and records a farmer must use or may wish to use; laws and regulations applicable to agricultural employers; and programs in which a farmer must participate.

Forms and Records '

Application for work Job descriptions Disciplinary action reports Termination forms Time cards Employee information forms

Laws and Regulations

Agricultural Labor Relations Act Unions

Industrial Welfare Commission Wages and hours

California Labor Code , Minors. discrimination

California Occupational Safety and Health Act Safety

Programs

Workers compensation insurance Disability insurance

ADDITIONAL INFORHATION

Safety forms. accident reports Payroll deducations forms Insurance forms Employee handbook Work permit for minors Posting of forms and notices

California Administrative Code Transportation of workers

State Vehicle Code Transportation of workers

California Health and Safety Code Field sanitatton

Unemployment insurance Social Security

The Cooperative Extension program of the University of California conducts public service educational activities in agriculture. home econom:i.cs and for youth.

Objectives include the improvement of agriculture through practical application of new methods and scientific knowledge to local needs and conditions. The work is supported cooperatively by county, state, and federal funds and is adminis-

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tered and staffed in counties throughout the state by the .University of California.

Loca1 field experiments I tests, demonstrations, meet.i.ngs ~ newslet.ters, and calls are used for introducing new methods of production ana se~king solutions for local problems.

Cooperative Extension provides literature and information developed by the University of California, United States DepartlDent of Agriculture, and by local staff members.

Publications are available that cover some of the information in this publication in more detail. They include the following subjects:

Fertilization Diseases Pest Control Propagation Orchard Evaluation Financial Analysis Statistics and Outlook Costs of Production

No endorsement of named products is intended products which are not mentioned.

Starting New Orchards Irrigation Soil Fumigation Weed Control Varieties Estate Planning Orchard Development Costs Thinning Avocados

nor is criticism implied of similar

Cooperative Extension work in Agriculture and Home Economics, Division of Agricultural Sciences, University of California, and United States Department of Agriculture cooperating. Distributed in furtherance of the Acts of Congre~s of May 8, a~d June 30, 1914. James B. Kendrick g Jr., Director, Cooperative Extension.

The University of California Cooperative Extension in compliance with the Civil Rights Act of 1964, Title IX of the Education Amendments of 1972, and the Rehabilitation Act of 1973 does not discriminate on the basis of race, creed, religion, color, national origin, sex, or mental or physical handicap in any of its programs or activities. Inquiries regarding this policy may be directed to: Affirmative Action Officer, UniversJty of California, 2120 University Avenue, Berke.ley, CA 94720, (415) 644-4270.

DOR/ch 30Dc

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