Horne, C. Wendell

Lee, Jr., Thomas A.

McCoy, Norman L.

Philley, George L.

Texas A&amp;M Repository

~ - :2.0- fB..1463'5~ ~Texas Peanut Diseaseand Nematode ControlRecommendations~ Texas Agricultural Extension Service. The Texas A&M University System. Zerle L. Carpenter, Director. College Station, Texas1984 TEXAS PEANUT DISEASE ANDNEMATODE CONTROL RECOMMENDATIONS .Thomas A. Lee,]r., C. Wendell Horne,Norman L. McCoy and George L. Philley·Peanut growers experience disease and nematodelosses in their crops each year. Disease and nematodecontrol recommendations in this publication are basedon well documented research and demonstration findings.The economic benefit of these recommendations relatedirectly to each grower's adaptation to soil conditions,crop sequence, water availability and climatic conditions.SEEDROTANDSEEDLINGDISEASECONTROLPlant high quality seed treated with a suggested seedprotectant fungicide. Seedling disease is less severewhen soil temperatures average 70° F. or more at a2-inch depth at 7 a.m. Suggested dry seed treatmentfungicides include Maneb-Captan, Botran-Captan,Arasan, Vitavax-Captan or Difolatan. Suggested flowableseed treatments are Pro-Ized II (Botran + Vitavax) andPro-Ized III (Botran + Vitavax + Thiram).A seed treatment product known as ABG 4000(Gustafson) is available which contains bacterial cellsthought to impart a condition which may aid incontrolling certain soilborne diseases. Studies areincomplete and future recommendations will be depen-dent on conclusions drawn from scientifically conductedinvestigations.Planter box treatment with materials such as Captanis suggested where seedling disease is prevalent. Useaccording to label directions.Vitavax used on Spanish peanut seed may causemarginal leaf burn and reduced seedling vigor. Runnerpeanuts have not been affected. Increased vigor usually isassociated with Vitavax on runner peanuts.• Extension plant pathologists, The Texas A&M University System.FOLIAR DISEASE CONTROLLeafspotsCombine chemical and cultural approaches. Rotatingwith other crops reduces disease organisms in the soiland makes chemical disease control more effective andprofitable. Use fungicides within their individualcapabilities. Control methods are listed:Irrigated peanuts - Spanish -Begin applications 35 to40 days after planting and continueat intervals until 20 to 21 daysbefore harvest, depending on thefungicide used and weather con-ditions.F/orunner - Begin applications 60to 65 days after planting unlesslate leafspot is a problem at anearlier stage. Continue as withSpanish.Dryland peanuts - Follow the same recommendationsas for irrigated pea"nuts if rainfallis sufficient for continuous plantgrowth and disease development.Under reduced moisture conditionsbegin fungicide applications atthe first evidence of leafspot orwhen rains or dews favor diseasedevelopment. Early detection ofleafspot requires close observation.Continue applications at suggestedintervals through periods suitablefor leafspot development. (Dewformation is most consistent inthe fall, beginning in September,but may occur anytime.) See table1 for chemical recommendations.Table 1. Recommended fungicide applicationintervals.SuggestedMaximum Can be usedsuggested as livestockfungicideinterval feed?Bravo 10-14- NoDifoJatan 10-14- NoManzate-200 or Dithane M-45 10- NoBenlate + Manzate 200" orBenlate + Dithane M-45 10-14- NoTopsin-M 10-14- NoSuper Tin"- 7-14- NoDu-Ter"- WP or WS 7-10- No30F.... 7-10- NoTop Cop 7-10- YesKocide 404 S 7-10- YesKocide 101 7-10- YesSulfur Dust 7- YesSulfur Flowable 7- Yes• Shorter intervals are necessary when disease pressure is great andweather conditions favor infection.•• Addition of nonphytotoxic oil (60 to 70 viscosity) may increase COntrol.DO NOT MIX BENLATE +MANZATE 200 + OIL COMBINATIONSWITH OTHER MATERIALS••• Triphenyltinhydroxide, the active ingredient in both Super Tin andDu-Ter, causes a mild foliage burn under some conditions. Irrigationapplication at beginning of set eliminates this burn. Do not mix thesewith any other spray material. Yields are not affected by slight burn.•••• Du-Ter F formulation only recommended through irrigation waterAlways read and follow labels carefully.Chemicals suggested for:Leafspot - Any of the above materials or approvedcombinations.Rust - Bravo, Benlare + Manzate 200 + oil orDithane M-45 (use shorter intervals).Web blOtch - Materials cleared for control of webblotch on peanuts include Benlate-Manzate200-oil-combination and Bravo.RustThe occurrence of peanut rust is geographicallylimited and sporadic but can become serious in areas ofSouth Texas during certain years. The fungus has notbeen observed over-wintering in Texas, and each yearspores must be blown in from the Caribbean area. Onceestablished during the growing season, rust can developrapidly in peanut fields. Apply fungicides effectiveagainst rust at regular intervals at the first sign of rust inthe field or in nearby fields. See table 1 for chemicalrecommendations.Potential Tolerance to FungicidesTolerance of the leafspot fungus to benomyl has beenreported in some parts of the United States. Eventhough this has not been awidespread problem in Texas,consider preventive steps. Tolerance develops when ahighly selective fungicide with a narrow spectrum ofcontrol is used extensively. One spore out of a billionmay tolerate the fungicide and not be controlled. Whenthis spore's offspring is not affected by the fungicide itcontinues to reproduce. After several reproductive cycles,large numbers of tolerant spores may be present in thefield. Use of a narrow spectrum fungicide can permit atolerant strain to develop, but it does not cause it.Development of tolerant strains can be reduced withone of two approaches:1. Alternating selective fungicides (benomyl) withnon-selective fungicides (chlorothalonil, tri-phenyltin hydroxide or others).2. Tank mixes of selective fungicides with othernon-selective fungicides (Benlate + Manzate200).Application MethodsFoliar fungicides may be applied with ground or airequipment in spray or dust formulations. Any methodthat evenly deposits the protective fungicide over theentire leaf surface is satisfactory. Ground spray equip-ment is popular. Use the suggested amount of fungicidein 10 to 15 gallons of water per acre, depending on vinesize. Use three open-cone nozzles per row spaced foroptimum coverage. Use 5 gallons of water per acre whenapplying fungicides by air.To control foliar disease and reduce early season costsmake the first three applications with ground equipment.If a three-nozzle arrangement is used, with one nozzle atthe top and two on the sides, plug the side nozzles for thefirst application and use only the top one. Use twonozzles on larger peanuts 10 to 14 days later by pluggingthe top one and using the two side nozzles. For the thirdapplication and throughout the growing season use allthree nozzles even though this may damage some vines.Careful use of ground equipment has little adverse effecton yield.Demonstrations conducted during the last 3 yearswith Control Droplet Applicators (CDAs) have shown ahighly acceptable level of control at total spray volumesas low as 1 gallon per acre. It is logical to consider theseunits as another method of ground application withunits spaced at approximately 40 inches on the boom.Demonstrations under field conditions show thatfoliar fungicides applied through sprinkler irrigationsystems give control equal to those applied by air andground equipment. Positive injection of fungicide isnecessary for application through center pivot irrigationsystems. Continuous agitation of fungicide-water com-binations required during the hours the center pivotsystem circles has caused some problems with fungicidesettling. This is not a problem with side-roll or hand-move systems.Aerial application of foliar fungicides provides goodcontrol. Adequate flagging insures even distribution andavoids swathwidths that are too wide. Stop spraying ifthe wind is high enough to cause excessive drift or ifspray droplets dry before they hit target plants. Stopapplication if temperatures are above 90° F. and relativehumidity is below 45 percent. A visible blanket of spraymixture will appear behind the aircraft when the 5-gallon-per-acre rate is used. This water rate is recom-mended for optimum control.POD, PEG AND STEM FUNGALDISEASE CONTROLSouthern Blight ControlCultural methods of controlling southern blightinclude:• Burying crop reside with a moldboard plow deepenough to avoid bringing it back up during landpreparation and cultivation.• Controlling leafspot with fungicides to preventleaf shed. Fallen leaves serve as a good source forthe southern blight organism.• Planting on a raised bed. Plant dryland peanuts ona slightly raised bed and irrigated peanuts on a bedapproximately 4 inches high.• Using a herbicide to prevent development of weedand grass residues that may serve as a good sourcefor the southern blight fungus.• Not throwing soil to peanuts during cultivation.• Digging when mature.Chemical control of southern blight is possible withVitavax or PCNB (Terraclor) when used correctly.Demonstration work in Texas during the last 5 yearsshows that Vitavax has more ability to knock down anexisting problem; however, Terraclor seems to beeffective longer than Vitavax. Consider these charac-teristics when selecting a chemical.Demonstration work applying PCNB or Vitavaxthrough sprinkler irrigation systems shows excellentresults. Southern blight was controlled and yields wereincreased where this disease was limiting production.Both products are labeled for application throughsprinkler irrigation systems in Texas. Follow labeldirections for application.Positive disease identification is necessary to get goodeconomic returns from chemical control. For example,PCNB is effective against the southern blight fungus butwill not control Pythium pod rot fungus. Use chemicalcontrol only when southern blight has been identified asthe limiting soilborne disease.Pythium Pod and Root RotThese diseases are controlled by:• Avoiding excessive irrigation.• Rotating with nonrelated crops. If possible, summerfallow during rotation. Use rye or oats as a wintercover crop. Turn this under deeply with other cropresidue in the spring. Plant on a raised bed.• Improving drainage in low areas.• Pythium pod rot is difficult to control. Successwith fungicides has not been sufficient to justifyrecommending their use. Applications of gypsumreduce pod rot where sodium salt accumulations inthe soil or irrigation water are high enough toincrease the pod rot problem.Rhizoctonia Pod Rot and Diplodia Collar RotRotating with nonrelated crops lowers populations ofthese organisms in the soil. Diplodia has been less severein plots where leafspot was controlled with fungicidesand where soil temperatures were reduced by vineshading. Plant rye or oat cover crops and turn themunder long enough before planting to accomplish initialdecomposition. PCNB controls Rhizoctonia when usedfor southern blight control.NEMATODE CONTROLDetermine whether enough plant parasitic nematodesare present to cause damage. Send a soil samplerepresentative of damaged area, along with peanut podsif available, to: Plant Nematode Detection Laboratory,Texas Agricultural Extension Service, College Station,Texas 77843. Information sheets are available at countyExtension ofices. Apply recommended nematicides whenplant parasitic nematodes limit production.Use caution when selecting a nematicide since soilmoisture is extremely critical. The fumigant-typenematicide, Telone II, works best when shanked 10 to 12inches into loose soil that is just a bit on the dry side (butnot extremely dry) for the top 3 to 6 inches. Excessivesoil moisture limits movement of the fumigant in thesoil, thus reducing effectiveness and possibly causingplant stunting. All fumigants give fewer problems whenapplied at least 10 to 14 days before planting. Granularnematicides work best with good soil moisture conditionson the surface where they immediately contact moisturenecessary for their activation. As moisture conditionsvary from planting season to planting season, growersmust consider these moisture requirements whenselecting a nematicide. Specific suggested materials arelisted in table 2.AFLATOXIN (SEGREGATION III)Aflatoxin is produced by a fungus, Asperi[!.illus flavus.Most infection and aflatoxin accumulation occur in thesoil before digging. Research shows some fields have ahigher population of this fungus than others. If peanutsTable 2. Nematicide.MaterialDichloropropene-Telone IICarbofuran (JO% granule)Furadan lOGAldicarb Temik (15% granule)Aldicarb Temik (15% granule)Phosphorothioate Dasanit 15GFenamiphos Nemacur 3Fenamiphos Nemacur 15GManufacturerDowFMC and MobayUnion CarbideUnion CarbideMobayMobayMobayRecommendationsFumigant4.5 to 6· ga/acre. Inject 10 to 12 in deep in well-prepared soil, not excessivelywet. Allow 7 to 14 days before planting, longer time for colder soilsContact20 to 40 Ib/acre incorporated into top 3 to 6 in over row. Do not feed treatedpeanut foliage to dairy animals or animals being finished for slaughter.14 to 20 Ib/acre in 6 to 12 in band preplant or at planting, incorporated 2 to4 in. Do not feed hay or vines to livestock.5 to 7 Ib/acre in 6 to 12 in band at planting incorporated 2 to 4 in. Plus, 10Ib/acre over row at peg with light incorporation. Do not feed hay or vinesto livestock.Band 13 1/3 to 262/3 Ib/acre (36 in row spacing) incorporate at plantingor preplanting. Do not feed hay to livestOck.Band 2 to 3.3 qt/acre (36 in row spacing) incorporate at planting. Broadcast1 to 1.7 gal/acre incorporate at planting. Do not feed hay to livestock.Band 10 to 17 Ib/acre (35 in row spacing) incorporate at planting. Broadcast20 to 33.5 Ib/acre incorporate at planting. Do not feed hay to livestock.• Demonstration work shows that maximum rates and placement depths result in excellent control of root knot nematodes.Data collected under Texas conditions are not sufficient to allow recommendations of other nematicides marketed for peanuts.from a field have this condition consistently, considerrotating with other crops. Peanuts under drought stressare more susceptible to field infection. Avoid thiscondition by irrigating, if this option is available. Duringthe season, control insects or other forms of pod injury.When soil temperatures range from 800 to 1000 F.and peanut kernel moisture drops below 25 percent,conditions for fungal development are ideal. Hot soilsreduce growth of some organisms antagonistic to A.flavus. Reduced kernel mositure and high soil tempera-tures before harvest usually increase segregation IIIpeanuts.Some mold damage and aflatoxin accumulationdevelop during harvesting and curing. Use inverterdiggers to keep pods off the soil surface while curingwithin the window. Adjust combines to prevent poddamage and transport peanuts in vented trucks andtrailers to prevent heating. Force air through the truckor trailer. Dryas soon as possible according to recom-mended procedures.VARIETY OF TYPE CHARACTERISTICSPeanut varieties differ in their susceptibility to diseaseorganisms. Although both runner and Spanish peanutsare affected by Pythium pod rot and southern blight, therunner types suffer the most damage. Give runner typesextra consideration when chemical treatments arerequired.Both Spanish and runner peanuts can be heavilydamaged by root knot nematodes; however, the extra 30days needed to mature the runner type magnifies theirdamage potential. Split applications of nematicides maybe more necessary for the runner variety.Foliage disease organisms attach both Spanish andrunner varieties. Spanish varieties are more susceptibleto web blotch. Cercospora or early leafspot can devastateboth types but is usually worse on Spanish varieties.With the extended growing season of runner peanutsand their partial tolerance of early leafspot, late leafspotoften is the most predominant foliage disease on them.Consider all these factors when planning a sprayprogram.OTHER DISEASE PROBLEMSAspergillus nigerAdditional disease organisms, for which there areinadequate control recommendations, pose a real threatto some peanut producers in Texas. One of these which,for the lack of a better name, will be referred to as "blackmold" and is caused by the fungus Aspergillus niger.This fungus can cause plant death at any stage fromseedling to harvest. The fungus attacks the crown orcollar area near the soil line and soon girdles and kills theplant. The black, slightly fluffy growth at the ground lineis the best field diagnostic symptom.Sc/erotinia sp.Another disease caused by a species of the fungusSclerotinia and referred to as sclerotinia blight wasobserved for the first time in Texas peanuts in 1981.Characterized in the early stages by small white tufts ofcottony-like growth on the stems near the ground line,the fungus spreads rapidly. Later stages of the diseaseshow up as severe plant stem shredding, almost as if thestems had exploded, accompanied by the production ofmany small, black, irregular-shaped sclerotia that are.approximately the size of mustard seed. The distinguish-ing field diagnostic symptom is plant death, accompaniedby stem shredding. At first glance many may confuse thisdisease with southern blight, caused by the fungusSclerotium rollsii. This mistake can be devastatingbecause chemicals that control southern blight have noeffect on sclerotinia blight.The Texas Department of Agriculture granted atemporary, special local-need Section 18 label for theUpjohnCompany product, Botran, and the BASF product,Ronilan, for Mason and surrounding counties for 1983.It is hopeful that these labels can be expanded andrenewed for 1984 and succeeding years. A multi-yearrotation, in conjunction with deep burial of crop residue,would also be helpful. Reports from other states andobservations from Mason, Texas, show the Sclerotiniaproblem is more severe on florunner than Spanishvarieties and then only after complete ground cover isachieved. Allowing the soil to dry out with theaccompanying temperature increase also appears to help'control the organism.Virus DiseasesTomato Spotted Wilt (TSW) and Peanut MottleVirus (PMV) are the two most common virus problemsin Texas peanuts. Neither is known to cause significantdamage. TSW causes reduced plant size in conjunctionwith a spotted, wilted plant. It is transmitted by thrips.Control of alternate host weeds in and around the fieldshelps control the problem.. PMV is probably the morecommon virus disease. It is characterized by slightcupping and irregular growth of leaves. When held up tothe light, leaves display a mottled appearance. There is alow level seed transmission of this virus.The information given herein is for educational purposes only. Reference to commercial products or tradenames is made with the understanding that no discrimination is intended and no endorsement by theCooperative Extension Service is implied.Educational proRrams conducted by the Texas ARricuiturai Extension Service serve people ofallaRes reRardleJI ofsocioeconomic level. race. color.sex. religion. handicap or national oriRin.Cooperative Extension Work in Agriculture and Home Economics, The Texas A&M University System and the United States Department ofAgriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8,1914, as amended, and June 30,1914.5M-2-84, Revision PP

1984 Texas Peanut Disease and Nematode Control Recommendations.

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1984 Texas Peanut Disease and Nematode Control Recommendations.

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1984 Texas Peanut Disease and Nematode Control Recommendations.

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