Vol . 14, No. 2 MaY 1980

THE NATIONAL PECAN MAGAZTNE

IBVol.

OUARTERLY

ISSN

14, No. 2 May I601700

THIS TIME:3 Pecan Weevil Management in

Texas

16 Reduce Blue Jay Damage

17 Monitoring Saves Time andMoney

19 Pecan Carry Over Lower ThanLast Year

2l Texas Pecan Growers to Meet inAbilene

26 A Critical Appraisal of PecanBreeding Priorities andProspects

DEPARTMENTS

13 Coming Up

14 Around the Pecan Belt

22 Research Notes

25 Can You Top This One . .

Oar Cover-This beautiful tYPical

cluster of pecans moY not be os

desirable os we have thought. It has

been an evolutinary insuronce policy inthe wild, but it also serves as a dfficultto change broke on yield ond regularbearing in commercial orchards. See

article by Wolstenholme andMalstrom on page 26.

PECAN ORCHARDCONSULTANT

oAssistance in selectingorchard sites

oEstablishing producingorchards

oHelp increase yield throughproper management advice

Jack A. MeyerRoute l, Box 68-'4'

Washington, Texas 77 880

7 13/878-2935

THE PECAN QUARTERLY is published quarterly by the Texas Pecan Growers Association, ll04 Winding Road, College Station, Texas incooperation with the Federated Pecan Growers Association of the United States. Address all communications to Drawer CC, College Station, Texas77841. Second class postage paid at College Station, Texas 77840. Pecan Growers Associations are educational organizations designed to keepmembers informed about the latest industry developments. Anyone interested in pecans is eligible for memberShip. Subscription rate for the Quarterlyis I year, $3.00; 2 years, $5.00; and 3 years, $6.00. Closing date for advertising copy 6 weeks preceding month of publication.

EDITOR: J. Benton Storey

Review Editor: Howard Malstrom. Southeastern Regional Editor: Charles Bruce. State Editors: Louisiana, Warren Meadows; Georgia, Tom Crocker;Mississippi, Clinton Graves; Florida, Timothy Crocker; Alabama, Harry J. Amling; South Carolina, James B. Aitken. Southwestern Regional Editor:George Madden. State Editor: California, Steven Sibbett; Arizona, Eugene Mielke; New Mexico, Jeanne Gleason; Oklahoma, Herman Hinrichs;Kansas, Frank Morrison; Texas, George McEachern.

CREDIT: Material in the publication may be used without permission if contentsCredit line to The Pec'an Quarterly will bc apprcciated.

2

are unrelated and not used so as to construe advertisins.

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San Saba, Texas 76877

915-372-3737

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t Dealer Prices on Pecan Chemicals

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FOR SALE: Bowie pecan harvesterin excellent condition, $3,000. Ownerdeceased. Contact Anton White,Route 2, Box 95, Cisco, Texas76437.Telephone 817 / 442-2496.

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Del Rio, TX 78840, Phone 512/774-2777.

May 1980

PECAN WEEVIL' MANAGEMENTIN TEXAS'

MARVIN K. HARRIS2, D. R. RING2,B. L. CUTLER2, C. W. NEEB3

, ANd J. A. JACKMAN4

Pecan weevil problems are pri-marily created by the pecan growerin the way the orchard or groveis managed. When pecan weevilproblems are especially severe, thegrower has done an excellent jobof managing pecan trees so theywill produce a good supply of nuts ona regular basis, but an inadequate jobof pecan weevil management.Research over the past several yearshas shown that solutions to the pecanweevil problem are available withconventional and traditionalapproaches (2, 3, 8). Regrettably, noeasy cure-all has yet been found,although significant refinements willcertainly be forthcoming in thefuture due to research currently inprogress. The purpose of this paper isto report on recent research findingswhich should assist the grower in

rCurculio caryae (Horn) (Coleoptera:Curculionidae)

2Department of Entomology, Texas Agri-cultural Experiment Station, The TexasA&M University Syst€h, CollegeStation, TX 77843.

3Area Entomologist, Texas AgriculturalExtension Service, The Texas A&MUniversity System, Fort Stockton, TX.

aSurvey Entomologist, Texas AgriculturalExtension Service, The Texas A&MUniversity System, College Station,TX 77843.

5Approved by the Director of the TexasAgricultural Experiment Station as TA16061.

The Pecan Quarterly, Vol . 14, No. 2

making pecan weevil managementdecisions. The approach will be toassess the aboriginal pecan/pecanweevil interaction and compare thatwith the cultivated condition andfinally to discuss how specificmanagement decisions can be made.

Aboriginal Pec an/Pecan WeevilInteraction

Wild pecans are notorious for theirirregular bearing patterns. This"boom and bust" pattern is usuallywidespread and relativelysynchronous in nature so that wildtrees in a given river bottom bear aharvestable crop every 5-8 years or so

with significantly fewer nutsproduced during the bust years.Reasons for this are complex and willnot be addressed here; suffice it to say

it occurs and that it has an effect onthe pecan weevil.

The pecan weevil is an obligatorynut feeder on pecan and hickory( I ,5 ,7 ,17, I 8). The pecan weevilfemale seeks out and lays eggs in nutswhen they are between the gel stage

and shuck split. If nuts are still in thewater stage, both males and femalesfeed on them causing them to drop. Asingle female will lay about 60 eggs,

placing, on the average, 3 or 4 eggs ineach nut she infests. She will notattack nuts that have been previouslyinfested. This adaptation probablyensures that the larvae which develop

in each infested nut have adequatefood to complete their development,even in years when weevilpopulations are high and nutsupplies are low. Larvae emerge fromthe nuts about 42 days after thefemale laid the eggs. The leglessgrubs drop from the nut and enter thesoil near the spot where they land.About 90Vo of the weevils whichsurvive will emerge as adults 2 yearslater to repeat the cycle. Theremaining lU%o will emerge 3 yearsafter entering the soil as larvae. Thegeneralized life cycle of the pecanweevil is shown in Fig. l.

Since wild trees usually producelow numbers of nuts, the pecanweevil usually exists in lowpopulations in the wild. When theoccasional heavy crop of nuts isproduced, the pecan weevil ispresented with more nuts than it caninfest and a reasonably good crop ofpecans can often be made despite thepresence of the weevil. The weevilpopulation does begin to build up inthe heavy crop year but then is"starved" back to low levels againduring the series of lean years whichusually follow bumper crops on wildtrees.

Cultivated Pec an/P ecan WeevilInteraction

Cultivated pecan differs from wildpecan in many ways. The mostimportant difference in relation to

Figure 2a

Figure 2. The female pecan weevil cannot successfully infest pecan nuts beforethey enter the gel stage. (a) The nuts shown are in late water, early gel stage; notethe shell formation, the "skin" or testa of the kernel and the thickening liquidendosperm (commonly called "water") which will form the kernel. (b) Note thedifferent stages of nut development based upon variety. (c) Oviposition occursprimarily on the distal third of the nut (end furtherest from point of attachment tothe cluster) where the kernel begins to form first. Obtaining a good longitudinalsection through a nut is done by cutting across the elliptical wound left when thenut was removed from the cluster. Cutting longitudinal sections in other planes fail

'to give good exposure to the developing kernel and make inspection difficult.

pecan weevil is that cultivated pecans(both improved and native) aremanaged with the intentioo, ifpossible, of producing a heavy cropof pecan nuts each year. In the case ofnewly planted orchards, pecan weevilmust invade the orchard after itcomes into bearing (about 3 to 5

years after planting). Generallyspeaking, pecan weevil adults do notmove very far in any great numbersso that the initial infestation of largeyoung orchards occurs when a fewweevils wander in. This earlyinfestation may pass virtuallyunnoticed due to the rapidlyincreasing crops of nuts producedeach year and the 2 to 3 years theweevil needs to complete eachgeneration (see Fig. l). As much as 4

or 5 years may pass after the initialinfestation of a new orchard has

occurred before nut productionbegins to level off a little bit. By then,the pecan weevil populations havehad an opportunity to increase toquite high levels. Suddenly, pecanweevil larvae appear to be in everynut.

A similar scenario can be drawnfor rehabilitated wild trees which arereferred to as "natives ". If the

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COMMON PECAN WEEVIL L IFE CYCLE

Figure 1. The Pecan weevil requires 2-3 years to complete an entire generation. The majority ofthe population requires 2years, as shown above, and those taking 3 years accomplish this by remaining in larval diapause an additional year. The

common 2 year life cycle means that events concerning pecan weevil last year have no bearing on problems in the current year.

Events 2 years ago influence what happens this year, and events this year primarily influence what happens 2 years from now.

May 1980

increased management (fertili zer ,

zinc, pruning, etc.) needed to bringthese trees into regular bearing is

begun following a series of leanproduction years, the pecan weevilpopulation in the grove is likely to be

low and scattered. Again, theincreasing nut production obtainedin the first few years of managementmay outstrip the pecan weevilsability to manifest itself in largenumbers. Within 3 to 5 years though,weevil populations have usually risento unacceptable levels.

In order to experience bad Pecanweevil probleffis, a grower must be

able to produce a reasonable crop ofpecans on a regular basis so the

weevil population has anopportunity to increase in numbers.Growers with severe pecan weevilproblems should not despair, for inall likelihood, only the pecan weevilstands between them and makin g aprofit; and, the pecan weevil can be

managed.

Pecan Weevil Management on Pecan

in Texas

The pecan weevil damages Pecansin 2 ways; first, adult feeding on nuts

in the water stage results in nuts

dropping off the tree and second,

females placing eggs in nuts results inlarvae which consume the kernel (3).

Adult feeding damage is far less

important than larval damage

because the latter not only mins the

nuts which are infested, but also

forms the nucleus of subsequentinfestations which will occur 2 and toa lesser extent 3 years later (see Fig.l). Since serious weevil Problemstend to originate within the orchardor grove , the long term solution to

weevil problems must revolve aroundreducing larval infestations to low

levels. A total commitment to thisend is required before one can have

any hope of preventing all damage.Reducing larval PoPulations

involves the prevention of ovipositionby killing adult weevils after they

emerge from the soil but before they

lay eggs in the nuts. There is a windowin time of about 3 to 5 daYs after agiven female weevil has emerged

The Pecan Quarterly, Vol . 14, No. 2

from the soil before she begins layingeggs. This is usually referred to as thepreovipositional period.

There is no feasible way to killadults or larvae while they are still inthe soil (5), or eggs or larvae in the

nuts. Treatment must be directed at

the adults after they have emerged

from the soil but before ovipositiontakes place. Rates and chemicalrecommendations are available inthe literature (6,9, 10, I l, 13, 16).

The pecan weevil female cannot

successfully oviposit until the nut has

passed through the water stage and is

in the gel or dough stage. The

oviposition window extends from the

gel stage to shuck split, although, oS

will be seen, the Period of greatest

risk is usually as the nuts are entering

the gel stage and shortly thereafter(late Aug. to mid Sept.). Fig. 2 shows

nuts that have been sectioned toshow various stages of internal

Figure 2b

Figure 2c

development. The weevil cansuccessfully oviposit in nuts at anytime from gel stage to shuck sPlit(2,3,7,8,12). Therefore, it is safe todelay oviposition preventiontreatments until the earliest maturingvarieties or trees in the orchard have

passed through the water stage even

though pecan weevil adults have

emerged. However, if pecan weevilshave emerged and are present in the

orchard, treatment must begin on thevery day the nuts enter the gel stage ifoviposition is to be prevented.

Furthermore, treatments must be

continued if weevils continue toemerge from the soil after the initialtreatment is no longer effective. The

treatment interval dePends on the

residual activity of the insecticide.

100

80

60

40

20

10

AUG

Carbaryl has been the treatmentstandard, and research indicates thismaterial requires reapplicationabout every 8-12 days when weevilscontinue to emerge, depending onthe intensity of the infestation. If noweevils have emerged for the 4consecutive days preceding theanticipated time of retreatment,spraying operations may be halted.One should continue to check foremergence and, if it is found,beginning the treatments againshould be considered. Treatmentsshould be terminated when shucksplit begins.

Fig. 3 shows the time and rate atwhich adult pecan weevils normallyemerge from the soil. One can use

this graph to assist in making pest

management decisions asfollows: The vertical axis represents

the cumulative percent emergence ofthe pecan weevil populatio.n and the

horizontal axis represents time. Ifone wants to know what percent ofthe population normally emerges bya given date, the date in question is

found on the horizontal axis of Fig. 3and an imagin ary vertical line is

extended upward to a point where itcrosses the curved graph line. A lineextended horrzontally to the left willintersect the vertical line where thepercent adult emergence can be read.

On Aug. 2l for example, l0 percentof the population are expected tohave emerged. One can also use thegraph to find the date when a givenpercent of the population will

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30 10

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Figure 3. Typical cumulative percent adult emergence of pecan weevil from the soil through time observed when no droughtstress is present. This graph may be used to make a crude approximation of pecan weevil problems in a given orchard or groveas follows: 1) Trap emerging weevils in cages placed over soi\ 2) on the sample day you wish to predict the amount of weevilsleft to emerge, add up all the weevils caught in your traps through that date;3) find the cumulative percent ofweevils expectedto have emerged by that date on the graph; 4) divide the weevils actually caught by the cumulative percent expected todetermine how many weevils are expected to emerge beneath your traps during the season. For example, suppose we have 30cone traps covering a total of 210 sq. ft. which have captured 8 weevils through August 2lst; 8 weevils-r.l0 (the expectedcumulative percent emergence from the graph) equals 80 weevils which is the predicted population that will emerge beneaththe cages for the entire season. This is definitely an economic infestation requiring treatment (see text for additionaldiscussion).

May 1980

normally have emerged. Forexample, 50 percent of the weevilpopulation will usually have emergedby Aug. 31.

Fig. 3 should only be used as an aidto pecan weevil management and notas the sole basis for deciding when totreat for 3 primary reasons. l) Thestatistics used to generate this graphindicate that in a particular year thecurve may be moved in time from 3 to6 days, even when conditions areapparently ideal for weevilemergence. This reliability is stillpretty good, but it also means thatthe curve will not exactly predictwhen the population will emerge.2)When drought conditions occurduring the time of normalemergence, a portion of the pecanweevil population will be delayed inemergence until irrigation or naturalrainfall occurs.E*periments atHamilton, TX have shown thatnaturally occurring droughtconditions can delay a portion of thepopulation in emerging for as long as

60 days. We have also artificiallycreated drought conditions bykeeping the soil dry with a tentbeyond the time of normalemergence and then adding water tosimulate rain in September. Someweevils always were observed toemerge during the normal emergenceperiod , regardless of the severity ofthe drought conditions. Theseweevils emerged through soil cracksand root channels that happened tobe present in the dry hard soil. Theweevils which were delayed inemergence by the drought wereconfronted with a hard layer of drysoil between them and the soilsurface. Wetting this layer of hardsoil with rainfall or water changedthe soil condition so that it becamefriable and the trapped weevils couldemerge. Fig. 4 shows the ways pecanweevil emergence was affected bydrought conditions. Otherpermutations are possible, and thesesimply illustrate the principleinvolved.

All soils do not exhibit the same

characteristics of hardness in relationto drought. Our work was conductedin a 20 percent clay,36 percent sand,

The Pecan Quarterly, Vol . 14, No. 2

and 44 percent silt, soil; and, soilmoisture levels below 20 percentmade the ground seem like adobebricks. Soils with lower percentagesof clay will generally retain theirfriability longer than the soils inwhich we have studied pecan weevilemergence. To prove this to yourself,think of how a soil with a highpercentage of sand, a low percentageof silt and almost no clay wouldsoften and harden as it were wettedand dried. Weevils could probablyemerge through that kind of a soil ina normal fashion regardless ofdrought severity because such a soilis quite friable through a very widerange of soil moisture. Contrast thatsoil to one with a high percentage of

clay, intermediate in silt andintermediate in sand. Such a heavyclay soil would be very mushy whenwet and almost like concrete whendry. Drought conditions in the lattersoil would definitely delay emergenceof weevils that could not find rootchannels or soil cracks throughwhich to emerge. Most locations withpecan weevil infestations containsoils between these 2 extremes, andemergence is affected by droughtaccordingly. Of course, timelyirrigation can eliminate problemsassociated with delayed emergencedue to drought within the irrigatedarea. Irrigation will not affectneighboring unirrigated trees andweevils, and, depending on the

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Figure 4. Drought conditions can delay emergence of some adult weevils fromthe soil. Emergence under natural drought conditions at Hamilton in 1977 in thetop graph shows 7570 of weevils emerging during the normal period in Aug.-Sept.with the remaining 25Vo emerling following a rain in late Oct. Drought conditionswere artificially created with a tent in 1978 and this resultedin2i%o of the weevilsernerging during the normal period with the remainder emerging in late Sept. afterwater was added as shown in the bottom graph. Since drought only delays aportion of the pecan weevil population from emerging, both the normally emergingand the drought-delayed weevils pose a threat to pecan production and bothrequire managernent. The portion emerging and the portion delayed under droughtconditions are present and please see the text for additional discussion.

ARTIFICIAL DROUGHT

7t--zaTtttt ozzzJ e- WATER

proximity of such trees, someconsideration of preventing lateseason immigration of droughtdelayed weevils may be called for.Perimeter spraying may be sufficientin this situation. 3) Finally, Fig. 3

does not describe the populationdensity of pecan weevils in theorchard or grove. This must be

ascertained from the past history ofweevil infestations or from trapcatches in the growing season, ofboth. If heavy weevil populationswere encountered 2 and/or 3 yearspreviously, treatment is mostprobably warranted. But, emergencecages in the orchard will verify thatadult weevils are present andtreatment is needed.

Pecan Weevil Management Options

The first and simplestmanagement option is to assume thatsufficient weevils are present in theorchard or grove to cause economicdamage and treat 3 or more timesbeginning at gel stage of the earliestmaturing cultiv?t, repeatingtreatments at 8- 12 day intervals untilsometime in mid-September. Thebasic drawbacks here are that initialtreatments may begin earlier thannecess ?ty, critical treatments maynot concide with peak emergence(Aug. 29-Sept. 2), drought delayedpecan weevil emergence rnay not bedetected, and one isn't sure when it issafe to terminate treatments.

A second option is possible basedon the history of infestation withinthe orchard or grove. If more than1700 nuts,/acre were lost to pecanweevil larvae 2 years previously, theassumptions in the first option willgenerally apply and one couldproceed by initiating treatments atgel stage, as above, and terminatingthem in mid September whenemergence in Fig. 3 indicates. Basicdrawbacks listed above still apply.

A third option is to initiate a

trapping system to monitor theweevils in the orchard or grove anduse the additional data tosupplement the information used tomake your management decisions.This is discussed below.

The Pecan Quarterly, Vol . 14, No. 2

A simple trap design is provided inFig.5. Each such trap will coverabout 7.1 square feet. Traps shouldbe placed within the drip line of thetrees in late July, and checkingshould begin based on whenemergence is expected from Fig. 3.

Trapping considerations

The number of weevils one shouldtrap before economic damage isexpected and treatment indicateddepends primarily on the size of thearea being sampled and whether or

Figure 5. Design for a cone trap to detect adult pecan weevil emergence from thesoil. The screen is rolled out and cut in the half circle pattern shown. Then it isgrasped in the center of the straight side and set upright. The screen assumes a

natural cone shape and the 34" lathe is overlapped and the screen stapled to it. The6" rim forms the skirt of the cage which is covered with soil to hold the cage in place

in the field. The collection jar (a small size baby food jar is sufficient) sits on thetop of the cage and consists of a screw top with a hole in the lid which sets over thehole in the top ofthe cage. This lid should be secured with caulk. Thejar isthenscrewed onto the lid. Snap-lid clear plastic boxes also work well by cutting a holein the box away from the lid and setting it in the cage and caulking it down.Regardless of the type of top used, the screen top of the cage should be allowed toprotrude about half-way into the collection device as this virtually eliminatesweevils emerging into the device from leaving through the small hole by which theyentered.

ADULT PECAN WEEVIL TRAP

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Raney, H.0. and R.D. Eikenbary.weevils. J. Econ. Entomol.

1969. A Simplified trap for collecting adult pecan62: 722-723.

not the trapping area is trulYrepresentative of the orchard as awhole. Generally speaking, I weevilemerging in every 50 square feet ofarea withing the drip line during the

season is sufficient to warranttreatment. This density of weevilscan be conservatively exPected todestroy at least 5000 nuts,/acre and totriple the problem to be faced 2yeatslater determined as follows: A pe0an

weevil female will attack and ovipositin about20 nuts, laying 3 or 4 eggs ineach nut. This means about 250

females are required to destroy 5000

nuts. Since the sex ratio is known toapproximate I male for each female,500 weevils (male * female) per actewill destroy at least 5000 nuts. Aneven distribution of weevils across

the acre would result in I adultemerging from each 87 square feet;however, larvae primarily enter theoil within the drip line of the tree

canopy and adult emergence almostalways occurs there as well.Therefore, emergence cages are onlyplaced within the drip line and a 60Vo

canopy cove r / acre is assumedresulting in about I weevrl/50 square

feet. The 3 times increase of the

weevil problem 2 years later, if leftuntreated, is derived from field andlaboratory observations of mortalitywhich lead to the assumption thatabout l\Vo of the larval PoPulationentering the soil will emerge 2 years

later as adults.The cost of 500 weevil s/ acre

calculated to at least 5000 nuts,/acrelost in the present growing season.

This represents 56 lbs (90 nuts/lb) ofnatives and 83 lbs (60 nuts/lb ) ofimproved and if the former sell for75a a lb, and the latter for $1.00, theexpected loss would be $41.70 and

$83 per acre, respectively, plus losses

which result from the increasedpopulation 2 years later. Note thatsome losses due to adult feeding willalso occur and have not been

accounted for. These feeding losses

should be less than 1000 nuts,/acreand contribute less than anadditional $ lOlacre to natives and

$15/acre to improved dollar losses.

Clearly, even if one quibbles overthe prices or exact density of weevils

l0

or nuts attacked/female, etc., it doesnot take very many weevils to causeeconomic damage. In fact, so fewweevils are required to causeeconomic damage that the cost ofdetecting them can exceed the cost oftreatment, and even then, there isroom for error. Present economicaltechnology using traps is primarilylimited to l) ensuring that weevilemergence is underway in theorchard or grove at the timetreatment is contemplated , 2) thatemergence continues to occur so thatretreatment is justified and 3) todetect late emergence due to droughtor other factors.

Research efforts are underway todevelop trapping systems which willprovide more reliable measurementsof sub-economic and borderlineeconomic infestations. RayEikenb ary in Oklahoma (Entomol-ogy Dept., OSU, Stillwater, OK) andDavid Boethel in Louisiana(Entomology Dept., LSU, BatonRouge, LA) have done much of thisresearch (2) and have institutedcooperative research demonstrationswith growers and other researchers(including Texas). We hope theirwork will be developed for generalgrower use. Presently their systemrequires 120 cages (12 each under l0trees) checked every other day andtrap catches evaluated with astandard chart they provide todetermine if treatment is needed.Predictions are thought to be validfor about each 80 acres of orchard.These researchers have improved,revised a1rd simplified this system forthe past several years. We believe oneadditional modification needed is todelay the first treatment for weeviluntil the earliest maturing pecans areon the verge of entering the gel stage,even when the trap catches indicatethat treatment should occur earlier.With this modification, theEikenbary-Boethel System isprobably more accurate in assessingpecan weevil density than anydevised anywhere else, including theone described below. However, thenumber of traps required ( 120) andthe frequency with which they mustbe sampled (every other day), if the

system is to be effective, oftendiscourages growers from using it.

An alternative system calls for 30

cone cages placed, in late July, 6 to atree under each of 5 trees in the

orchard. The 5 trees should be thoseknown to contain pecan weevilpopulations of 2 years previously or,if their infested condition is

unknowD, the 5 trees should be

chosen to include early andintermediate maturing trees. Nutdevelopment of the earliest maturingtrees in the orchard or grove shouldbe followed closely so that the end ofthe water stage and the onset of thegel stage can be anticipated.

Timing of Initial Treatment

Cages should be checked once ortwice a week for weevil emergence

during this initial period and if anyweevils are found, an insecticidetreatment should be applied to theorchard or grove just when the gel

stage of nut development on theearliest maturing trees is reached. Ifpecan varieties have been planted so

each can be treated separately, thosevarieties still in the water stage can be

left untreated. Feeding damage willoccur at a rate of about .25

nut,/w eevil/ day on the untreatedtrees but oviposition will not occuruntil after the gel stage is reached (3,

8). If such pecans are initially leftuntreated, nut development on themmust be followed very closely toensure that they are treated when thegel stage begins. Any slippage pastthat point, and oviposition willoccur, thereby eliminating anysavings to be had in delaying thetreatment.

Feeding damage, in our opinion,has been unduly emphasized inproportion to present and futuredam age which results fromoviposition and larval infestation.The rate of feeding dam age has beencalculated at about .25 nuts/weevrl/day. Note in Fig. 3 that adultemergence from the soil does notreally get under way until the lastweek in August and note also that formost pecan varieties, gel stage doesnot occur until late August or

May 1980

September. Therefore, the bulk ofthe pecan weevil population is notsusceptible to insecticide treatmentuntil the pecan tree is at or near thegel stage, and the small proportion ofpecan weevils emerging earlier do notrepresent the damage potential yetlocome. For maximum effective ness,

the initial insecticide treatmentshould be directed at the most adultspossible, just prior to the pecan nutbeing susceptible to oviposition.Furthermore, if pecan weevilpopulations are so enormously highthat adult feeding damage prior tonormal gel stage of early maturingtrees (generally Aug. 24-30) is

economically important, then verypoor weevil control was obtain ed 2years previously. Avoiding this same

problem 2 years down the roadrequires preventing oviposition inthe current year. Proper timing of theinitial insecticide application andappropriate retreatment will preventoviposition and reduce subsequentfeeding damage,thereby protectingthe crop in the current year and

greatly reducing problems frompecan weevil 2 years later. Earlyinsecticide application to preventadult feeding damage should be

considered only if very highpopulations of adults are present andthe grower is totally committed topreventing oviposition by the bulk ofthe adult population which has yet toemerge from the soil. If thisargument is still unconvincing, andthe additional treatment(s) is used,this should only be necessary for the

. ,first 2' or 3 years of the program, sincepreventing oviposition will have

, resulted in substantially loweringpecan weevil populations (and hencetheir capacity to cause feedingdamage in the water stage) in lateryears.

Retreatment

The need for retreatment isdependent upon whether the weevilscontinue to emerge after the residualactivity of the insecticide is abated.Carbaryl is thought to provide

continued protection against weevilsemerging for at least 5 days or so

after treatment, barring rain washingthe treatment off earlier. Emergencecages should be emptied 4 days aftertreatment and checked again 3 dayslater for additional weevilemergence. If weevils are found,retreatment should occur within thenext 4 days. If no weevils are found,cages should be checked again 2 dayslater and if weevils have emerged,retreatment should occur within the

next 2 days. Whenever retreatmentoccurs, emergence cages should be

emptied 4 days later and checkedagain as before.

Fig. 3 provides a useful guide toanticip ate adult pecan weevilemergence from the soil as long as

drought conditions are not present.Note that even under idealemergence conditions, the spread inthe time of emergence requires a

minimum of 2 treatments for low buteconomic populations and probably3 for higher ones. Note also thatdrought conditions will delay aportion of the population inemerging for long periods of time. Ifdrought conditions are present in theorchard and weevil catches in thetraps fall to zero after the first orsecond treatment, do not relax.Continue checking the cages everyfew days and be immediatelyattentive following a droughtbreaking rain. Prior research has

shown that the majority of droughtdelayed weevils emerge within thefirst 3 days following a rain and thatdamage and oviposition can occur onup into November if shuck split has

not taken place.

Leonard Farms

Pecan Tree Nursery

Wichita Western Schley Cheyenne

all sizes

Contact: Floyd Gage

Leonard Farm Nursery

Route 1, Box 263

Brownwood, Texas 7680I

915/784-5845

t2 May 1980

Summary:

l. Use Fig. 3 to anticipate the time and rate of pecan

weevil activity unless drought conditions are present. Fig.4 shows how drought can affect emergence.

2. Place at least 30 pecan weevil emergence cages (6

each under 5 trees) in the orchard or grove in late July.3. Check nuts on early maturing trees for the cessation

of the water stage and the onset of the gel stage (see Fig.2).

4. Check pecan weevil emergence traps as gel stage ofnuts on earliest maturing trees approaches.

5. Spray at gel stage if weevils are found or, if weevilsare not found, continue to check traps at least every otherday and spray when weevils are found. If no weevils are

found by Sept. 15 and drought conditions were notpresent the preceeding 4 weeks, check traps twice a weekfor the next 2 weeks and if no weevils are found, terminatechecking.

6. Clean out emergence cages 4 days after each

treatment and check them again 3 days later; if weevilsare found retreat within the next 4 days; if no weevils are

found, check agarn 2 days later and if weevils are found,retreat within 2 days; if no weevils are found, continuechecking every other day until Sept. 15 and twice a weekfor 2 weeks thereafter, treating only if weevils are found.If no drought conditions were present the preceeding 4

weeks, the weevil problem can be considered over. Ifdrought is present, the final flush of weevils can be

expected within 3 days after the next rain and this shouldbe a matter of concern until shuck split is complete. Theemergence cages should reflect drought delayed weevilemergence and contain some adults if this occurs. Checkthem to verify this late emergence and spray if they are

found and shuck split has not occurred.

7. Remember, the pecan weevil oviposition window isfrom the gel stage to shuck split. Weevils normallyemerge early in this period about when most pecans are

entering the gel stage and these weevils must be preventedfrom ovipositing. Fig 3 depicts the normal pecan weevilemergence and if drought conditions occur during thisperiod, a portion of the population will be delayed inemerging until the drought is broken. Drought delayedweevils can be verified by emergence cages and will cause

damage if shuck split has not occurred.8. Usually 2 and often 3 properly timed treatments are

needed to control pecan weevil. Droughts during thenormal emergence period can result in delaying a portionof the population for 2 months or more. If this occurs,zfladditional treatment will be needed within 4 or 5 daysafter the drought is broken.

9. Rainfall following insecticide treatment but beforethe normal time for retreatment is necess ary depends onif weevils continue to emerge from the soil. If they do,retreatment within 3-5 days of the rain is called for toprevent ovipositon.

10. Ground application of insecticide has, in general,been better than aerial application for pecan weevilmanagement. However, satisfactory results have beenobtained by some growers as a supplemental means ofapplying treatments and in a few cases as the major modeof management. Both proper timing and coverage areessential to pecan weevil management. Aerial applicationcan improve timing where treatment areas are large andequipment scarce, or when muddy fields prevent entrywith ground equipment. This feature of improved timingcan, to some extent, outweigh the anticipated problem ofreduced coverage and should be considered.

Continued to page 14

July IThird Biennial Meeting of theCalifornia Pecan Growers, Visalia,California.

Third California Pecan

Growers Meeting Set

New and established Pecangrowers, growers interested inpotential for pecans and those

associated with pecans in Californiawill meet in Visalia, July l, 1980 forthe third meeting of this kind. The

The Pecan Quarterly, Vol . 14, No.

meeting usually on a biennual basis

was last held in 1978 when more than230 persons attended. Speakers frommany locations in the western states

will discuss economics, nutritioD,marketing, varieties, productionpotential and the concepts of a pecan

growers association. The meeting isorgani zed by Steve Sibbett andLyndon Brown, Tulare and KingsCounty farm advisors, respectively.

While in California, out-of-stateparticipants will visit severalestablished pecan plantings andother fruit and nut orchards. A winetasting and other social gatheringswill be provided by local growers.The interest in pecan culture has been

growing steadily over the past l0years in California.

July 14-16Fifty-ninth Anniral Conference,Texas Pecan Growers Association,Abilene Civic Center, Abilene.

August 14, 15, 16, 1980Annual International PecanConference, Hermosillo, So-nora, Mexico. For more infor-mation contact Ing. FranciscoTapia, Asociacion Agricola Lo-cal de Productores de Nuez,de la Costa de Hermosillo,Yucatan y Pino Suarez, Hermosillo,Sonora, Mexico.

l3

Continued from page l3

REFERENCES CITED

l. Aguirre-Uribe, Luis A. 1979. Biology ofthe immature stages of the pecan weevilCurculio coryae (Horn) and ovipositionhabits of the adult weevil. Ph.D. Disserta-tion. Texas A&M Univ. 72 p.

2. Boethel, D. J. and R. D. Eikenbary. 1979.Status of pest management programs forthe pecan weevil (PP8l-l l9). /n Pest man-agement programs for deciduous treefruits and nuts. D. J. Boethel and R. D.Eikenbary (Eds.) Plenum Press, NewYork. 256 p.

3. Calcote, V. R. 1975. Pecan weevil:Feeding and initial oviposition as relatedto nut development. J. Econ. Entomol.68:4-6.

4. Harris, M. K. 1973. Pecan weevillarval response to some temperatureswhile in the nut. TAES Progress ReportH3t76 (April). 3 p.

5. Harris, Marvin K. 1975. Pecan weevil dis-tribution in some Texas soils. J. Environ.Entomol. a(5):641-44.

6. Harris, Marvin K. 197 5. Principles ofconcentrate insecticidal spraying of fruitsand nuts. Tex. Pecan Orchard Manage-ment Handbook 197 4. pp 120-24.

7. Harrrs, Marvin K. i976. Pecan weevil in-festation of pecans of various sizes andinfestations. Environ. Entomol.5(2):248-50.

8. Harris. Marvin K. 1976. Pecan weevil adultemergence onset of oviposition andlarval emergence as affected by thephenology of the pecan. J. Econ. Entomol.69(2):167 -70.

9. Harris, Marvin K. 1979. Pecan weevil dis-tribution on pecan across the Pecan Belt.South. Coop. Ser. Bul. 238. Tex. Agric.Exp. Stn. College Station, Tex. 12 p.

10. Harris, M. K. and H. W. Van Cleave. 1974,Economic losses attributable to somepecan insects in Texas. WesternIrrigated Pecan Growers AssociationProceedings. pp. 57-62.

I l. Harris, Marvin K. and Luis Aguirre. 1978.Pecan, pecan weevil and hickory shuck-worm management, 1977. Insecticide andAcaracide Tests. 3:59-60.

12. Harris, Marvin K. and Dennis R. Ring.1979. Biology of pecan weevil fromoviposition to larval emergence. South-west Entomol. 4:73-85.

14. Harris, Marvin K., H. W. Van Cleave andG. M. McWhorter. 1978. Minimum pecaninsect management. Proc. Tex. PecanOrchard Management Short Course,98-105.

14. Harris, Marvin K., W. G. Hart, M. R.Davis, S. J. Ingle, and H. W. Van Cleave.1976. Pecan identification, defoliation,refoliation and nut yield in relation towalnut caterpillar attack on native pecans.Pecan Quart. l0(2): 12-18.

15. Hoelscher, Clifford 8., L. Reed Green,H. W. Van Cleave and Marvin K. Harris.1975. Pecan weevil: Where it exists in Tex-as. Pecan Quart. 9(\:2a-25.

16. McWhorter, G. M., J. G. Thomas, M. K.Harris and H. W. Van Cleave. 1976. Pecaninsects of Texas. TAEX. Texas A&MUniv. MP-1270. 18 p.

l4

the Pecan BeltAround

0/

A Word From Chihuahua, Mexico OnHigh-Density Plantings

I am not sold on close planting,with the idea of removing trees later.Many Mexicans cannot finance close

spacing for two reasons. One is the

extra cost of trees, and the other is thedifficulty in growing an inter-crop.We prefer to plant fewer trees, whichwill serve as our permanent trees, andinter-crop with corn, beans, peppers,and even cotton as long as we can.

Wider spacing allows the trees tospread more. I am in favor of toppingthe trees to prevent them fromgetting to such extreme heights,which would also help spread themmore.

Philip B. BrownAve. de Las Quintas No. 22

Parral, Chihuahua, Mexico

Pecans or Sycamores

Homer and Tom were long-timeneighbors, living on opposite sides ofthe street, east and west. A stormblew over two elm trees in Tom'sfront yard. Homer had four sizablesycamore trees in his west front yardwhich provided a dense shade.Sitting under Homer's trees onemorning, Homer said, "Tom, whydon't you set out some sycamores so

we can sit in your yard in theafternoon?" Tom said, "No, Homer,when I set more trees, they will bepecans." "Yeah, but it takes pecansso-o-o long to bear, Tom," Homersaid. Tom pointed to the sycamoresand asked, "How long will it takethese sycamores to bear?" Startled,Homer answered, "Come to thinkabout it-it will take quite a while,won't it?"

Thomas J. Renick357 Kirkwood Court

Dallas, TX 75232

@v17. Raney, Harley G., R. D. Eikenbary and

Newton W. Flora. 1969.Investigations ondispersal of the pecan weevil. J. Econ.Entomol. 62:1239-40.

18. Ring, Dennis R. 1978. Biology of thepecan weevil emphasizing the period fromoviposition to larval emergence. M.S.Thesis, Texas A&M University, CollegeStation, TX.

ACKNOWLEDGEMENTS

Research included in this paperhas been partially supported by theScience and Education Administra-tion of the U. S. Department ofAgriculture under Grant No.7800156 from the CompetitiveResearch Grants Office.

We are grateful for assistance inconducting this work obtained fromKirk Brown, Tom Haensly, TerryHensley, Ron White, BobbiLoveless, Terri Droste-Dowell, RemiOlszak, Brent Wiseman, NelsonBean, Luis Aguirre, Gloria Pravia,James Gagne , Cal Blanchard andRusty McDaniel. We appreciate thecooperation of Johnny Harris atHamilton, Elbert Hoffman ofLeonard FarffiS, The Kimble CountyPecan Growers Association, and thatof other growers whose cooperationwas essential in carrying out thiswork.

May 1980