read the sunflower production guide
TRANSCRIPT
The Sunflower Production Guide
The Sunflower Production Guide
TABLE OF CONTENTS
Acknowledgements 2
SunflowerIndustryProfile 3
INTRODUCTION
›GrowthStages 4
›FieldSelection 6
›Fertilizer 6
›Seeding 9
›FieldScouting 11
›Tillage 12
›Harvesting 12
Pest Management
Integrated Pest Management 13
Insects 14
›SeedlingandRootFeeders 15
›Wireworms 15
›Cutworms 16
›SunflowerBeetle 17
›ThistleCaterpillar 19
›InsectsintheStem 20
›SunflowerBudMoth 20
›SunflowerStemWeevils 22
›SunflowerMaggots 24
›InsectsontheHeads 26
›SunflowerMidge 26
›SunflowerSeedWeevils 28
›BandedSunflowerMoth 30
›LygusBugs 32
›BeneficialInsects 34
Diseases 37
›EarlySeasonDiseases 37
›DownyMildew 37
›FoliarDiseases 39
›Rusts 39
›AlternariaLeaf andStemSpot 41
›Septoria 42
›StalkandRoot-InfectingDiseases 42
›SclerotiniaWilt andBasalRot 42
›SclerotiniaMid-StalkRot 44
›PhomaBlackStem 45
›PhomopsisStemCanker 46
›VerticilliumLeafMottle 47
›HeadRotandDiseasesof MaturePlants 48
›SclerotiniaHeadRot 48
›Rhizopus 49
Blackbirds 50
Weeds 51
›Cocklebur 51
›BiennialWormwood 52
›CanadaThistle 53
›Kochia 54
›PrairieSunflower 55
›Wild-Buckwheat 56
›RedrootPigweed 57
›FalseRagweed 58
›GreenandYellowFoxtail 59
References 60
The Sunflower Production Guide
A|XXX
ACKNOWLEDGEMENTS
PHOTOGRAPHS:
Crop Staging A.A.SchneiterandJ.F.Miller,NorthDakotaStateUniversity
Insects JohnGavloski,ManitobaAgriculture,FoodandRuralInitiativesJanKnodel,NDSUExtensionService,DepartmentofEntomology
Diseases ThomasGulya,UnitedStatesDepartmentofAgricultureSamMarkell,NorthDakotaStateUniversity
Weeds NasirShaikh,ManitobaAgriculture,FoodandRuralInitiatives
ThisguidewasfundedinpartbytheCanadaandManitobagovernmentsthroughGrowing Forward,afederal-provincial-territorialinitiative.
2|Acknowledgements
The Sunflower Production Guide
XXX|A
SUNFLOWER INDUSTRY PROFILE
TheNationalSunflowerAssociationofCanada(NSAC),Inc.wasinitiatedatameetinginCarman,MBonNovember18,1996.ThemeetingwasorganizedtoaddresstheclosureofthesunfloweroilcrushingplantinAltona,MBin1995causingsunfloweracreagetodropfromahighofmorethan300,000acresduringthe1980’sto63,000acresin1995.Theacreagealsoshiftedtoconfectiontypes,promotedbyprocessorslocatedthroughoutManitoba’sRedRiverValleyandsouthernAlberta.
Theassociation’smissionstatementis“toinsuretheprofitabilityandlongtermgrowthofthesunflowercropthroughindustrywideleadership”.Membershipincludesproducers,oilandconfectiontypebuyers,exportersandprocessors,pesticidemanufacturersanddealerswithintheseedindustry.SincetheestablishmentoftheNSACin1996,sunfloweracreagehasclimbedto180,000acresin2008.In2011theassociationhadapproximately650membersfromManitoba,Saskatchewan,andAlberta.
Approximately90percentofallsunflowersgrowninCanadaarelocatedinManitoba,butagrowingshareisfindingitswayintosoutheasternSaskatchewan,southernAlbertaandsouthernOntario.OfallCanadiansunflowers,65percentareconfectiontypeswhicharemarketedprimarilyasroastedsnackfoodintheshellorasdehulledseedsforthebakingindustry.Althoughasignificantpercentageofthismarketisdomestic(NorthAmerica),CanadianprocessorsareincreasinglyaccessingmarketsinEurope,theMiddleEastandAsia.Oilseedsunflowersareusedinboththebirdfoodandthecrushingindustryforsunfloweroilproducingoneofthehighestqualityvegetableoils.Althoughthebirdfoodmarketismostlytheoilseedtype,someofthesmallerconfectionseedsarealsousedforbirdseed.
SunflowerIndustryProfile|3
The Sunflower Production Guide
4|GrowthStages
INTRODUCTION
GROWTH STAGES
Thetotaltimerequiredfordevelopmentofasunflowerplantandthetimebetweenthevariousstagesofdevelopmentdependsonthegeneticbackgroundoftheplantandthegrowingenvironment.Theaveragedevelopmentofalargenumberofplantsshouldbeconsideredwhendeterminingthegrowthstageofasunflowerfield.Laterintheseason,forstagesR-7throughR-9,usehealthy,disease-freeheadstodetermineplantdevelopmentsincesomediseasescancauseheaddiscoloration.Anumberorrecentlyreleasedandgrownhybridscontainthestay-greencharacteristic.Ifthischaracteristicispresent,yellowingorbrowningofthebractsmaynotbeanaccurateindicatorofplantmaturity.Maturityistypicallyreachedwithin2200-2300growingdegreedays(Celsius)afterplantingor120-150days.
Table 1. Sunflower growth stages and description
Stage Description
VE Vegetative Emergence Seedling has emerged and the first leaf beyond the cotyledons is less than 4 cm long.
V (number) Vegetative Stages (e.g. V-1, V-2, V-3 etc.)
These are determined by counting the number of true leaves at least 4 cm in length beginning as V-1, V-2, V-3, V-4, etc. If senescence of the lower leaves has occurred, count leaf scars (excluding those where the cotyledons were attached) to determine the proper stage.
R-1 Reproductive Stages The terminal bud forms a miniature floral head rather than a cluster of leaves. When viewed from directly above, the immature bracts have a many-pointed star-like appearance.
R2 The immature bud elongates 0.5 to 2.0 cm above the nearest leaf attached to the stem. Disregard leaves attached directly to the back of the bud.
R3 The immature bud elongates more than 2 cm above the nearest leaf.
R4 The inflorescence begins to open. When viewed from directly above, immature ray flowers are visible.
R5 (decimal) (e.g., R-5.1, R-5.2, R-5.3, etc.)
This stage is the beginning of flowering. The stage can be divided into sub-stages dependent upon the percent of the head area (disk flowers) that have completed or are in flowering. Ex. R-5.3 (30%), R-5.8 (80%), etc.
R6 Flowering is complete and the ray flowers are wilting.
R7 The back of the head has started to turn a pale yellow.
R8 The back of the head is yellow but the bracts remain green.
R9 The bracts become yellow and brown. This stage is regarded as physiological maturity.
From Schneiter, A.A., and J.F. Miller. 1981. Description of Sunflower Growth Stages. Crop Sci. 21:901-903
The Sunflower Production Guide
GrowthStages|5
Figure 1. Stages of sunflower development. (A.A. Schneiter and J.F. Miller)
North Dakota State UniversityFargo, North Dakota 58105
FEBRUARY 1998
A-1145
Stages of Sunfl ower Development
A.A. Schneiter, ProfessorJ.F. Miller, USDA-ARS
D.R. Berglund, Extension Agronomist
Vegetative Stages
R-5.1
R-8 R-9R-7
R-5.5 R-5.9 R-6
True leaf — 4 cm
V-E
V-2
V-4
R-3 R-3 Top View R-4 Top View
R-1 R-2
Reproductive Stages
V-12
R-2 R-3
More than 2cm
Less than 2cm
The Sunflower Production Guide
6|Introduction
FIELD SELECTION
Soils
Sunflowersgrowbestonwelldrained,highwater-holdingcapacitysoilswithanearlyneutralpH(pH6.5-7.5).Theoptimumsoilclassificationsforsunflowersareloam,siltyloamandsiltyclayloamsoils.Sunflowerproductionperformanceonreducedagriculturalcapacitysoilssuchasthoseaffectedbysalinity,droughtpotentialorwetness,isnotideal,butcompareswithofothercommonlygrowncommercialcrops.
Crop rotation
Havingapropercroprotationalsequenceisimportantwithallcrops,includingsunflowers.Extendedcroprotationshelpreducediseaseinoculumloadsinthesoil,allowforherbiciderotation,manageoverwinteringinsectpopulations,weeds,waterusageandfertilitymanagement.
Growerswhodonothaveadequatecroprotation,willlikelybeconfrontedwithoneormoreofthefollowingyield-reducingproblems:
� Diseaseanddisease-infestedfields(e.g.increasedsclerotinia)� Increasedinsectrisk� Increasedpopulationsofcertainweedspecies� Increasedpopulationsofvolunteersunflowers� Soilmoisturedepletion� Allelopathyorphytotoxicityofthesunflowerresiduetothesunflowercrop
FERTILIZERGeneral
Germinatingsunflowerseedsareverysensitivetoseed-placedfertilizer.Starterapplicationsshouldbeplacedawayfromtheseed.Whensunflowersareseededwithrowequipment,allphosphateandpotassiumshouldbesidebanded2"besideand2"belowtheseedduringplanting.Someorallofthenitrogencanalsobesidebanded.Thetotalamountoffertilizermaterialsidebandedshouldnotexceed300lb/ac.
Nitrogenapplicationscanbemadepre-plant,atseeding,post-seeding,side-dressoracombinationofthesemethods.Applicationshouldbetimedsonitrogenisavailableforrapidplantgrowthanddevelopment.Often,itislogisticallyadvantageoustoapplynitrogeninthefall.However,thelongerthetimeperiodbetweenapplicationandplantuse,thegreaterthepossibilityforNloss.Fallapplicationisnotrecommendedinsandysoilssincetheopportunityforleachingismuchgreater.Aside-dressapplicationofNwhenthesunflowerplantsareabout12incheshighisoftenpreferable.
The Sunflower Production Guide
Introduction|7
Phosphateandpotashmaybefallorspringappliedbeforeatillageoperation.Thesenutrientsarenotreadilylostfromthesoilsincetheyattachtothesoilformingonlyslightlysolublecompounds.Phosphoruscanbeappliedpreplant-broadcast,preplantbanded,orbandedatseeding.Bandappliedapplicationsaremostefficient,especiallywhenonlysmallamountsareappliedinfieldslowinavailablephosphorus.Potassiumdeficienciesnormallyonlyoccurinsandysoils.Potassiumthatisbandplacedisabouttwiceasefficientasbroadcastapplications.
Table 2. Nutrient uptake and removal by sunflower in Manitoba studies.
Nutrient Uptake Removal Uptake Removal
lb nutrient for a 2000 lb crop lb nutrient per cwt
Nitrogen (N) 74-122 48-66 3.7-6.1 2.4-3.3
Phosphorus (P2O5) 24-56 18-26 1.2 – 2.8 0.9 – 1.3
Potassium (K2O) 150-172 18-26 7.5 – 8.6 0.9-1.3
Sulphur (S) 8-12 3-4 0.39 – 0.58 0.17-0.22
Calcium (Ca) 54-94 3-4 2.7-4.7 0.15-0.23
Magnesium (Mg) 37-39 6-7 1.86-1.93 0.30-0.36
Fertilizerapplicationsshouldbemadebasedonasoiltest.RecommendationsbasedonsoiltestingweredevelopedbyManitobaAgriculture,FoodandRuralInitiatives(MAFRI)andarelistedinTables3and4.Recommendationsarebasedona0-24"samplefornitrate-nitrogenandsulphate-sulphur.Phosphorusandpotassiumarebasedona0-6"sample.
Table 3. Nitrogen recommendations for sunflower (based on spring band application).
TARGET YIELD (lb)
Fall Soil NO3-N 1750 2,000 2,250 2,500
lb/ac in 0-24" Rating Nitrogen Recommendations (lb/ac)
20 VL 40 85 125 170
30 L 20 60 105 145
40 M 0 35 80 120
50 M 0 10 55 100
60 H 0 0 30 75
70 H 0 0 5 50
80 VH 0 0 0 25
90 VH 0 0 0 0
100 VH+ 0 0 0 0
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8|Introduction
Table 4. Phosphorus, potassium and sulphur recommendations for sunflower based on soil test levels and placement.
PHOSPHORUS POTASSIUM SULPHUR
Soil Phosphorus (0-6")
Fertilizer Phosphate (P2O5) Recommended (lb/ac)
Soil Potassium (0-6")
Fertilizer Potash (K2O) Recommended (lb/ac)
Soil sulphate-Sulphur (0-24")
Fertilizer Sulphur (S) Recommended (lb/ac)
ppm lb/ac Rating Sb2 ppm lb/ac Rating Sb2 PPI3 lb/ac Rating N/A3
0 0 VL 40 1 0 VL 30 60 0 VL 20
5 VL 40 25 50 VL 30 60 5 VL 20
5 10 L 40 50 100 VL 15 30 10 VL 20
15 L 35 75 150 L 15 30 15 L 20
10 20 M 30 100 200 L 0 0 20 L 20
25 M 20 125 250 M 0 0 25 M 20
15 30 H 15 150 300 M 0 0 30 M 20
35 H 10 175 350 H 0 0 35 H 0
20 40 VH 10 200 400 VH 0 0 40 VH 0
20+ 40+ VH+ 10 200+ 400+ VH+ 0 0 40+ VH+ 0
Sb2 = Side Banded Adapted from the Manitoba Agriculture Food and Rural Initiatives.
PPI3= broadcast and pre-plant incorporated
N/A3= placement does not influence effectiveness of sulphate forms of sulphur fertilizer
Plant Tissue Analysis
Planttissueanalysisisanimportanttoolinassessingnutrientstatusofthegrowingcrop.FollowingareplanttissueanalysisinterpretivecriteriausedbytheformerManitobaAgricultureProvincialTestinglaboratory(Table5).Theselevelsshouldbeusedforthetoponetothreemostmatureleavesatthebudstage.However,ifadeficiencyisdetectedatthisstage,yieldpotentialhasalreadybeenaffected.Thissamplingmethodisbestusedasanauditingtooltodetermineifyourfertilityprogramissufficientfortheyieldpotential.Ifanutrientdeficiencyisobservedearlier,sampleplantsandsoilfromtheaffectedareaandcontrastresultswithplantandsoilsamplesfromanadjacent,normallookingarea.Thisisconsidereddiagnosticsamplingandcouldbeusedtocorrectsomein-seasondeficiencies.Consultwithyoursoilandplanttissuelaboratoryforguidelineswhensamplingatothergrowthstages.
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Introduction|9
Table 5. Sunflower tissue analysis interpretation
CONTENT
Nutrient Low Marginal Sufficient High Excess
Nitrogen % N 1.4 1.5-1.9 2.0-3.4 3.5-3.9 4.0
Phosphorus %P 0.14 0.15-0.24 0.25-0.49 0.5-0.79 0.8
Potassium %K 0.9 1.0-1.4 1.5-2.9 3.0-4.9 5.0
Sulphur %S 0.14 0.15-0.19 0.2-0.39 0.4-0.99 1.0
Calcium %Ca 0.19 0.2-0.29 0.3-1.9 2.0-2.4 2.5
Magnesium %Mg 0.09 0.1-0.19 0.2-1.4 1.5-1.9 2.0
Zinc ppm ZN 11 12-14 15-69 70-149 150
Copper ppm (Cu) 2 3-5 6-24 25-74 75
Iron ppm (FE) 14 15-19 20-249 250-499 500
Manganese ppm (Mn) 9 10-14 15-99 100-249 350
Boron No provincial guidelines developed. Consult analytical companies
Special Fertility Considerations
Sunflowershavedeeptaprootsthatcanobtainwaterandnutrientsfivetosixfeet(1.5to1.8meters)deepinthesoil.Thesereservesofwaterandnutrientsareunavailabletomostotherannualcrops,makingsunfloweragoodrotationalcrop.Sunflowershavetheabilitytoscavengenitrogenthathasleachedbelowtherootingdepthofothercrops.
SEEDING Planting dates
SunflowerseedingshouldusuallybeginanytimeafterMay1andideallybecompletedbyJune1.Seedlingsarerelativelyfrosttolerantuptothefour-leafstage.ChooseearliermaturinghybridsoroiltypehybridsifplantingisdelayedintothefirstweekofJuneorforreplanting.Oiltypehybridsareshortermaturingthanconfectionvarieties.Plantingdatecanalsoaffectsusceptibilitytopests.Consultthefollowingchaptersastowhentoplanttoavoiddamagebythemostprevalentpestinyourarea.
Plant Populations and Row Spacing
Seedingrateforsunflowersdependsonsunflowertype.Oilseedvarietiesaregenerallyplantedathigherpopulationsthanconfectionaryvarieties.Oil-typesunflowerpopulationsrangefrom20,000to22,000plants/acre(0.6plants/ft2).
The Sunflower Production Guide
10|Introduction
Plant Populations and Row Spacing (Continued)
Confectiontypesunflowersshouldnotexceed18,000plants/acre(0.4plants/ft2)toensurelargeseedsize.Seedingratesforbothoilandconfection-typesunflowersshouldbeadjustedwhengerminationislow.Refertotables6and7forinformationonplantdensityandrowspacingaswellasseedsizeandweight.
Noyielddifferenceshavebeendetectedbetweensunflowersseededinrowsversussolidseededwhenadequateweedcontrolexists.Fieldswitharowspacinglessthan20inchesareconsideredtobesolidseeded.Recommendedrowspacingforsolidseedingis10to12inches(25.4to30.5centimeters)forbothconfectionandoil-typesunflowers.Plantpopulationsshouldremainthesameasstatedaboveregardlessofrowspacing.Equidistantplacementofseedswithintherowallowsformaximumutilizationofresources(e.g.water,nutrients,sunlight)andoftenresultsinconsistentheadsize.Sunflowerplantscompensatefordifferencesinplantpopulationsbyadjustingheadandseedsize.Asplantpopulationsincrease,headandseedsizedecreaseandviceversa.
Depth
Sunflowersneedtobeplacedinmoisturebutnotdeeperthanthreeinches(7.6cm).Theidealseedingdepthis1½to2inches(3.8to5cm)deep.Plantingequipmentshouldfirmthesoilovertheseedrowtomaintainamoistseedbedandensuregoodseedtosoilcontact.
Table 6. Seed spacing required for various populations, assuming 90 percent germination and 10 percent stand loss
ROW SPACING (inches)
Plants/acre 12 16 18 22 30 36
--------- Seed spacing within row (inches) ---------
14,000 30.2 22.6 20.2 16.5 12.1 10.1
16,000 26.5 19.8 17.6 14.4 10.6 8.8
17,000 24.9 18.6 16.6 13.6 10.0 8.3
18,000 23.5 17.6 15.7 12.8 9.4 7.8
19,000 22.3 16.7 14.9 12.2 8.9 7.4
20,000 21.2 15.9 14.1 11.5 8.5 7.1
21,000 20.2 15.1 13.4 11.0 8.1 6.7
22,000 19.2 14.4 12.8 10.5 7.7 6.4
23,000 18.4 13.8 12.3 10.0 7.4 6.1
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Introduction|11
Table 7. Sunflower seed size and associated seed weight
OIL-TYPE SUNFLOWER CONFECTION SUNFLOWER
Seed Size Seeds/lb Seed Size Seeds/lb
No. 2 5,000 – 6,000 Medium 4,000 – 5,000
No. 3 6,000 – 7,000 Large 3,000 – 4,000
No. 4 7,000 – 9,000 Extra Large 2,000 – 3,000
FIELD SCOUTINGSunflowerareahosttoanumberofpests.Fieldsshouldbemonitoredregularlyforpotentialproblems,todeterminepestspeciespresentandifpopulationsareateconomicthresholdlevels.Fieldscoutinginvolveswalkingintothefieldandassessingtheoverallhealthofthecrop.Sunflowerpeststendnottobedistributedevenlythroughoutafield,sofieldsshouldbecheckedinseverallocations.Forexample,somepestsaremoreabundantnearthefieldedgesratherthaninconcentratedareaswithinthefield.Determiningtheextentofapestpopulationonthebasisofwhatisfoundinonlyoneortwosmallareasof afieldisimpossible.Samplingsitesshouldbeatleast75feetinfromthefieldmargin.Todeterminewhetheranentirefield,oraportionofthefield,requirestreatmentatleastfivesitesper40-acresshouldbemonitoredtocollectadequateinformationonthenatureandextentofapestinfestation.ThepaththroughthefieldshouldfollowtheZorXpatternasshowninFigure2.
Figure 2. The X and Z scouting patterns (NDSU)
The Sunflower Production Guide
TILLAGEManytillageregimesarepracticedinCanadaincludingconventional,strip,ridge,minimumandzero-tillage.Manyfactorsaretobeconsideredwhendecidingwhattillageregimetoutilize,includingsoiltype,climate,fertilizerregimeandrotation.Differenttillageregimesareassociatedwithdifferentimpactsoncropproductionandtheenvironment.Forexample,conventionaltillagecanbeutilizedtocontrolspecificcroppests,howeveritisalsoassociatedwitherosion.Minimum-orzero-tillagecanbeimplementedtomanageerosionandpreservethesoilprofile.Anunderstandingofthebenefitsanddrawbacksofeachtillageregimeisimportantwhendecidingwhichtoutilize.
HARVESTINGTiming
Sunflowersareusuallythelastcroptobeharvestedinthefallsincefallfrostshelpindryingdownthecrop.Theperiodbetweenmaturityandharvestshouldbekeptasshortaspossibletominimizelossesfrombirddamageandhead-rotdiseases.
Desiccation
Chemicaldesiccationisusedtoquickendry-downofsunflowerheads.Desiccationiseffectivebeforeakillingfrostinenhancingheaddry-downbutshouldnotbeappliedbeforethebackofthesunflowerheadturnsyellowandthebractsarebrownanddry.Thebracttipsturnbrownat40-50%seedmoisturewhichisstilltoohighfordesiccation.Propertimingiswhenmostofthebractshaveturnedbrown.Atthisstagetheplantisphysiologicallymatureandseedmoisturewillbe20to50percent.RefertothecurrentGuidetoCropProtectionfordetailsondesiccationproducts.
Combining
Sunflowerscanbecombinedwhentheseedmoistureisbelow20percent.Harvestingwhenseedmoistureisgreaterthan20percentcanresultinscuffingduringharvestingandshrinkageduringdrying.Itwouldbepreferabletocombineseedsat10to13percentmoisture.Sunflowerscaneasilyshatterifheadsareverydry,andthereforecombinespeedmustbeslowedaccordingly.Cylinderspeedsrangefrom300-500(rpm),withconcavesettingsquiteopen(oneinchinfrontand¾ inchinrear)tominimizeseedbreakageanddehulling.Usingtheslowestcylinderspeedswiththelargestopeningwillresultintheleastseeddamage.
Harvesting Attachments
Combinesthataresuitableforharvestingsmallgrainswillbeadequatetoharvestsunflowers.Aproperheaderattachmentisnecessarytoreduceshatteringlossesandharvestefficiency.
12|Introduction
The Sunflower Production Guide
Therearetwotypesofattachments:
� Thepanheaderwhichismountedontraditionalstraightcutheadersandissuitableforbothrowcropandsolidseeding.
� Theallcropheader,whichisonlysuitableforrowcropplanting.
Storage
Sunflowerseedissafetostoreatamoisturecontentof9.5percentorless.At10to12percentmoisturecontent,seedcanbestoredinbinswithaeration.Anymoisturecontentover12percentwillrequiredrying.Oil-typesunflowerscanbedriedwithtemperaturesof71-104°C(160-220°F)butconfectiontypesmayscorchorwrinklewiththesetemperatures.Sunflowerseedshouldbecooledbeforestorage,sinceevensunflowersat8.5percentmoisturecanspoilifstoredwhenwarm.
PEST MANAGEMENT INTEGRATED PEST MANAGEMENT IntegratedPestManagement(IPM)isasustainableapproachtomanagingpestsbycombiningbiological,cultural,physicalandchemicaltoolstominimizeeconomic,health,andenvironmentalrisks.Anumberoffactorsinfluencetheabundanceanddiversityofpestsfromyeartoyear.Controlmethodsvaryineffectiveness,butintegrationofdifferentpestmanagementtoolscanminimizepestnumbersandthecostofmanagementwithoutunnecessarycroplosses.IPMmaximizestheeffectivenessofchemicalpesticides,whileminimizingtheimpactonnon-targetorganismsandtheenvironment.
Scoutingforpotentialpests,monitoringfieldsandkeepingnotesofpestincidencesanddensitiesisrequiredtodetermineiflevelsareapproachingtheEconomicInjuryLevel(EIL)ortheEconomicThresholdLevel(ETL).Economiclossesarearesultofpestnumbersincreasingtowheretheycausecroplossesgreaterthanorequaltothecostofcontrollingthepest.TheEIListhenumberofpestsatwhichtacticsmustbeappliedtopreventanincreasingpestpopulationfromcausingeconomiclosses.TheETListhelevelofpeststhatwillcauseeconomicdamageandisoftenlowerthattheEIL.TheETLvarieswithcropprice,yieldpotential,cropdensity,costofcontrolandenvironmentalconditions.Pestsshouldbeidentifiedaccurately;controlmeasuresandeconomicinjurylevelsdifferbetweendifferentorganisms.Recognizingbeneficialorganismsisimportantastheyhelpreducenumbersofdamaginginsects,whichthenmaynotrequireadditionalcontrol.
Significantprogresswithinsunflowerpestmanagementstrategieshavebeenmade,andwillcontinuetobemadeintothefuture.Asnewcropmanagementstrategiesaredeveloped,itisimportanttoweighcropproductionbenefitsversusenvironmentalimpacts.
IntegratedPestManagement|13
The Sunflower Production Guide
INSECTS Thefollowingsectionsprovidecurrentinformationonmanagementofinsects,diseases,weedsandbirds.BelowisagrowingseasoncalendarthatshowsthemajorsunflowerpestproblemsandtimeofoccurrenceinthenorthernGreatPlainsproductionarea(Figure3).
Figure 3. A growing season calendar indicating time of occurrence of major sunflower pests. (J. Knodel, NDSU).
14|IntegratedPestManagement
APRIL MAY JUNE JULY AUGUST SEPTEMBER OCTOBER
Crop Stages
Weed Control
Insects
Diseases
Birds
Emergence Vegetative Bud Flowering Mature
CutwormsPalestriped Flea Beetle Budworm Moth Budworm – 2nd Generation Longhorned Beetle (Dectes) Stem Weevil Sunflower Beetle Adults Larvae Adults Sunflower Maggot Adults Larvae Sunflower Moth Adults Larvae Banded Sunflower Moth Adults Larvae Seed Weevil Lygus Bug Head Clipping Weevil Sunflower Midge Grasshoppers
Blackbirds
Downy Mildew White Mold, Rust, Verticillum Wilt Apical Chlorosis Phoma Black Stem Head Rot Alternaria Leaf and Stem Spot Premature Ripening
Preplant and Preemergence Post Emergence Final Weed Survey
CONTROL TIPS Iftheriskofwirewormdamageishigh,seedscanbetreatedwithanapprovedinsecticideforprotectionofgerminatingseedsandseedlings.ConsultthecurrentGuidetoCropProtection.Norescuetreatmentsareavailableforcontrollingwirewormsafterplanting.
Figure 4. Wireworm larvae
4
The Sunflower Production Guide
SEEDLING AND ROOT FEEDERSWireworms
Wirewormlarvaefeedongerminatingseedsoryoungseedlings.Infestationsaremorelikelytodevelopwheregrasses,particularlyperennialgrasses,havebeengrowing.Stemsofyoungseedlingsmayemergeshreddedanddamagedplantsmaysoonwiltanddieresultinginthinstands.
Host Crops
Grasses,corn,carrots,potatoes,wheat,barley,pulsecrops,sunflowers,andmanyothercrops.
Biology
Wirewormlarvae(Figure4)areslender,smoothandhard-bodiedwire-likeworms varyingfrom1.5to2inches(38-50mm)inlengthwhenmature.Theyhave3pairsoflegsbehindthehead,areyellowishwhitetoacopperycolorandthelastabdominalsectionisflattenedandnotched.Itusuallytakes3to4yearsforwirewormstodevelopfromaneggtoanadultbeetle.Mostofthistimeisspentasa larva.
Boththewirewormadultsandlarvaoverwinterdeepinthesoil.Larvaemoveupanddowninthesoilprofileinresponsetotemperatureandmoisture.Aftersoiltemperatureswarmto50°F(10°C),larvaefeedwithin6inches(15cm)ofthesoilsurface.FromlateMaythroughJunethefemalebeetleslay200to1400eggsinloosesoilandunderlumpsofsoil.Whensoiltemperaturesbecometoohot(>80°F,27°C)ordry,larvaewillmovedeeperintothesoiltoseekmorefavorableconditions.Duetothis,wirewormsinflictmostoftheirdamageinearlyspringwhentheyarenearthesoilsurface.
Scouting Techniques
Soilsamplescanbecollectedandsievedinthespringtofindwirewormspresentinthefield.Soilshouldbesampledtoadepthof15cm(6inches)andrepeatedindifferentareasofthefieldtodeterminetheaveragenumberoflarvaepersquaremeter.Baitscanalsobeusedtoattractwirewormstoanareaformonitoring.Thepasthistoryofafieldisagoodindicator,especiallyifwirewormshavebeenaprobleminpreviousseasons.Croprotationmayimpactpopulationlevels.
Insects|15
The Sunflower Production Guide
Cutworms
Cutwormscanbeaseriousprobleminmanyfieldcrops.Therearemanydifferentspeciesinvolved,butthemostcommonaretheredbacked,darksidedanddingy cutworms.
Host Crops
Theredbackedcutwormfeedsinmostfieldcrops,vegetablesandhomegardenplants.Itisbestknownforfeedingoncereals,flax,canolaandmustard.
Biology
Cutwormlarvae(Figure5)havefoursetsofabdominalprolegsandcurlupwhendisturbed.Redbackedcutworms(Euxoa ochragaster)havetwobroadredorreddish-brownstripesthatextendstheentirelengthofthebody.Thetop-stripesaredividedbyadarklinewithwhiteinthecentre.Theheadisyellowish-brown.
Darksidedcutworm(Euxoa messoria)larvaearewhiteontheventralsidesandpalebrowndorsally.Theyhavenumerousindistinctstripes.Dingycutworm(Feltia jaculifera)larvaearedullbrown,withamottlecreamcolor.Thedorsalareaispalewithtracesofobliqueshading.
Cutwormmothsmaylayseveralhundredeggsinoronthesoil.Aftertheeggshatch,thelarvaefeedonthehostplants.Larvaenormallyhave6instarstages.Theymoultseveraltimes,eventuallyreachingaboutfivecentimeters(2inches)inlength.Thelarvaetunnelintothesoiltoformearthencellswheretheypupate andnewlyemergedmothsexitusingtheoldlarvaltunnels.Somespeciesoverwinteraseggs(e.g.theredbackedcutworm)oraslarvaeorpupae.StillothersdonotoverwinterinthePrairiesbutratherre-invadeannuallyfromtheU.S.,aidedbysoutherlywinds.Onegenerationofthisspeciesisproduced peryear.
Scouting Techniques
Cutwormsarenocturnal,feedingatnightandhidingduringthedaymakingthemhardtodetect.Oncethecrophasemerged,continuescoutingonaweeklybasisfrommid-Maytomid-June.Feedingbycutwormsresultsinnotched,wilted,deadandcut-offplants(weedsorcropseedlings).Plantsmaybemissingfromrowsandbarepatchesmayappearinfieldsasaresultofcutwormfeeding.Usingasmallgardentrowelandasoilsifter,cutwormscanoftenbefoundinthesoilaroundplantstheyhaverecentlydamaged.Cutwormsmaybe founddowntoabout5cm(2inches)belowthesoilsurface.Thesmall,worm-likelarvaecurluporattempttohideinthedebris.Pupaemayalsobecollectedinthisway.
16|Insects
Figure 5. Different species of cutworm larvae.
CONTROL TIPS Bestresultsoccurifinsecticideapplicationsaremadeintheevening.Sometimesitismosteconomicaltojusttreatinfestedpatchesandnottheentirefieldastherearedifferencesinsusceptibilitytoinsecticidesbetweenspeciesofcutworms.ConsultthecurrenteditionofGuidetoCropProductionforregisteredinsecticides.
Youngcutwormlarvaemaybestarvedbeforespringseedingbyallowingvolunteergrowthtoreach3to5cm(1.2to2inches),cultivatingandthenseeding10to14dayslater.Manypredaceousinsects,parasitesandbirdspreyuponcutwormsandreducetheirpopulations.
The Sunflower Production Guide
Economic Thresholds
Treatmentiswarrantedwhencutwormdensitiesexceed1cutwormpersquarefoot(30cmx30cm)orifthereisa25to30%standreduction.
Sunflower Beetle
Feedingbyadultbeetlesandlarvamayresultinpoorseedset,seedfilling,reducedyieldsanddelayedmaturity.
Host Crops
Sunflowerbeetlesfeedonnativeandcultivatedsunflowers.
Biology
Adultsunflowerbeetlesthorax(areabehindthehead)isapalecream-coloratthetopwithareddish-brownpatchatthebase.Eachwing-coverhasthreedark-brownstripesthatextendthelengthoftheback.Thefourthstripeendsatthemiddleofthewinginasmalldotthatresemblesanexclamationpoint.Sunflowerbeetlelarvae(Figure7)areyellowishgreenwithabrownheadcapsuleandhumpbackedinappearance.Newlyhatchedlarvaeareabout1.5to1.75mm(1/16inch)longandwillgrowtoabout8to10mm(underhalfaninch)whenfullydeveloped.
5
Insects|17
Figure 6. Adult – Sunflower beetle
Figure 7. Larva – Sunflower beetle7
6
The Sunflower Production Guide
Biology (Continued)
Sunflowerbeetlesoverwinterasadultsinthesoil.Usually,theiremergencefromthesoilinthespringcoincideswiththetimethatsunflowerseedlingsbegintoappearinlateMay.Thebeetlesfeedthroughoutthedayontheemergingseedlings.Eggshatchaboutaweekaftertheyarelaidandtheyounglarvaefeedontheleavesatnight.Theyhideamongthebractsoftheflowerbudandintheaxilsoftheleavesduringtheday.Thelarvaefeedforabouttwoweeks,butbecauseofthelongegglayingperiod,larvaemaybepresentinthefieldforaboutsixweeks.Thematurelarvaedroptotheground,enterthesoil,andpupateinearthencells.Thepupalstagelastsabouttwoweeks.AdultsofthenewgenerationemergeandfeedforashortperiodinlateAugustandearlySeptember.Theyfeedontheuppermostleavesorbractsoftheplantbeforere-enteringthesoiltooverwinter.
Scouting Techniques
Noticeabledamageisoftenfirstseenonplantsnearthemarginsofsunflowerfields.Whenplantsareseedlings,scouttodeterminetheaveragenumberofadultbeetlesperplant.Forlargerplants,determinetheaveragenumberoflarvaeperplantandpercentdefoliationbysampling20plantsat5sitesalonganXpatternforatotalof100plants.
Economic Thresholds
Thethresholdis1to2adultbeetlesperseedlingatthetwotosixleafstageor10to15larvaeperplantduringthesummer.Severeleafdamagemayoccurtoplantsinthetwotosixleafstageswhenadultbeetlesarenumerous.Controlmaybenecessaryifdefoliationcausedbyeithertheadultsorthelarvaereaches25to30percent,especiallyifmoredefoliationisexpected.Ifthemajorityofthelarvaehavereachedmaturityatabout25percentdefoliation,controlshouldnotbenecessary.
18|Insects
CONTROL TIPS Naturalcontrolsusuallykeepsunflowerbeetlepopulationsbelowdamaginglevels.Sunflowerbeetleeggsareeatenbythethirteenspottedladybeetleandtheconvergentladybeetle.Larvaeofthecommongreenlacewingconsumebotheggsandlarvae.Damselbugsandthetwospottedstinkbugmayalsopreyonlarvaeofsunflowerbeetles.Parasitoidsattacksunflowerbeetleeggs,larvae andadults.Insecticidesareavailabletocontrolsunflowerbeetle.ConsultthecurrenteditionoftheGuidetoCropProtectionforregisteredinsecticidesthatcontrolsunflowerbeetle.
8
9
CONTROL TIPS Insecticideusehasnotbeenwarantedforcontrolofthistlecaterpillar.
Figure 8. Thistle caterpillar
Figure 9. Painted lady butterfly
The Sunflower Production Guide
Thistle Caterpillar
Thistlecaterpillar(Vanessa cardui)hasbeenanoccasionalpestofsunflowers.Localizeddamageofsunflowercropshasoccurredduringsporadicyearsofhighpopulations.
Host Crops
OnCanadathistle,larvae(Figure8)feedselectivelyonfoliage,leavingonlythestemandmidrib.
Biology
Adults,commonlyknownaspaintedladybutterflies(Figure9),arriveonthePrairiesduringearlyJune,dependingonspeedandpatternofmigration,fromoverwinteringsitesintropicalandsubtropicalareas.Thereisnoevidencethattheycansurviveourcoldwinters.ThisbutterflylayseggsonCanadathistleandabroadrangeofhostplants.Larvaefeedontheleavesproducingloosewebbing.Thelarvaeareupto30mm(1.25inches)longanddarkpurpletoblackincolor.Theyhavelongspinesoneachsegmentoftheabdomen.
Scouting Techniques
Ifpopulationsseemheavywhilescouting,sampleabout100scatteredplants,notingthepercentdefoliationoneach.Dividethetotalpercentdefoliationbythenumberofplantssampledtoobtainanestimateofpercentdefoliationforthe field.
Economic Threshold
Thethresholdis25percentdefoliationprovidedthatmostofthelarvaearestillunder3centimeters(11/4inches)long.Ifthemajorityoflarvaearefullygrown,mostofthefeedingdamagewillhavealreadyoccurred.
Insects|19
Figure 10. Adult Sunflower bud moth
Figure 11. Sunflower but moth larvae
Figure 12. Entrance hole of larva
Figure 13. Larva feeding results in deformations of the sunflower head, often a hole is formed.
11
The Sunflower Production Guide
INSECTS IN THE STEM Sunflower Bud Moth
Highpopulationsofthispesthavebeenreportedinthepast.Despitehighpopulations,thesunflowerbudmothmaynotcausehighlevelsofeconomicloss.
Biology
Sunflowerbudmoths(Suleima helianthana)haveawingspreadofabout16to18millimeters(0.63 inches).Eachgray-brownforewinghastwodarktransversebands(Figure 10).Onebandextendsacrossthemiddleofthewing,andthesecondbandislocatednearthewingtip.Thelarva(Figure11)haveadarkheadcapsulewithasmooth,cream-coloredbody.
InManitoba,twogenerationsofsunflowerbudmothareproducedperyear.AdultsemergefromoverwinteringpupaeduringthelastweekofMaytomid-June.Afewdaysafteradultemergence,eggsaredepositedontheterminalsofimmaturesunflowersoronthereceptacleofmaturesunflowers.Eggsalsoaredepositedinleafaxils.Thehatchedlarvaebegintunnelingintothesunflowerplant.Theinitialinfestationinmid-Juneischaracterizedbyanentranceholesurroundedbyblackfrass(insectexcrement)(Figure12).Maturelarvaepupatewithinthesunflowerplant.Pupaemovetotheopeningoftheentranceholesformedinthestemorheadtissuesothatadultscanemergeeasily.ThesecondgenerationadultsappearinJulyandAugust.Infestationsbythesecondgenerationlarvaearenoteconomicallyimportant.
20|Insects
10
13
12
The Sunflower Production Guide
Insects|21
Inearlyplantedsunflower,mostoftheinfestationsoccurinthestalks,whereasinlateplantedsunflower,mostinfestationsoccurinthepithareasofthehead.Theonlytimeyieldlossisnoticeableiswhenlarvaeburrowintounopenedbuds,preventingproperheaddevelopment.Thelarvaenormallydonotfeedondevelopingseeds,butconfinefeedingactivitiestothefleshlypartofthehead.Despiteminimaleconomiclosses,thelarvacausemalformationsinboththeheadandstalk(Figure13).
Scouting Techniques
Afieldmonitoringschemeforthisinsecthasnotbeenestablishedsinceitisnotofeconomicsignificance.
Economic Threshold – Nonehasbeendetermined.
CONTROL TIPS Insecticideusehasnotbeenwarrantedforcontrolofsunflowerbudmoth.
The Sunflower Production Guide
Sunflower Stem Weevil
Therearetwomainstemweevilsspecies,theSpottedSunflowerStemWeevilandtheBlackStemWeevil.
Biology
TheSpottedStemWeevil(Cylindrocopturus adspersus)adultsareabout4to5millimeters(3/16inch)longandgrayishbrownwithvaryingshapedwhitespotsonthewingcoversandbetweentheheadandabdomen.Thesnout,eyesandantennaeareblack.Thelarvaeare5to6mm(1/4inch)longatmaturityandcreamywhitewithasmall,brownheadcapsule.ThelarvaewillnormallybeinacurledorC-shapepositionwhenfoundinsunflowerstalktissue.ThespottedstemweeviladultsemergeinmidtolateJuneandfeedontheepidermaltissueofthesunflowerfoliageandstem.Thisfeedingdoesnotaffectplantvigor.Matingoccurssoonafteremergenceofadults.Justpriortoegglaying,femalesdescendtothelowerportionoftheplanttodepositeggsindividuallyintheepidermaltissueofthestem.Eggsareverysmall(0.51mmlongby0.33mmwide).UponhatchinginearlyJuly,thefirstinstar(larvalgrowthstage)larvaefeedonsub-epidermalandvasculartissue.Feedingisconcentratedinthepithtissueasthelarvaedeveloptothirdandforthinstars.
BythelastweekinAugust,thelarvaehavedescendedwhilefeedingtojustabovethesoilsurface.Arudimentarychamberisconstructedinthestem,andtheweevilsoverwinterinthischamberasfifthinstarlarvae.PupationoftheoverwinteringlarvaoccursthefollowingyearinearlyJune.Thereisonegenerationperyear.
TheBlackStemWeevil(Apion occidentale)adults(Figure14)areblackandonly2.5mm(0.1inches)longfromthetipofthesnouttothetipoftheabdomen.Thesnoutisverynarrowandprotrudesforwardfromthehead,whichissmallinrelationtotheratherlargebody.Thelarvaeareverysimilarinappearancetothespottedstemweevilexcepttheyareonly2.5to3mm(0.1to0.12inches)longatmaturityandyellowishincolor.
Theblackstemweeviloverwintersasadultsinsoil,plantresidue,sodandweedclusters.Uponemergence,theadultsfeedonvolunteersunflowersintheearlyseedlingstage.Adultfeedingoncultivatedsunflowerbeginsatthetwo-tofour-leafstage.Femalesdepositeggsundertheepidermisofthestem.Larvaeemergingfromtheseeggstunnelinthepithareaofthestem,pupateandemergeasadultsinearlyAugust.
LittleornoadultactivityisobservedforabouttwoweeksinlateJulyandearlyAugust.ApionadultsemerginginAugustalsofeedontheleavesandstemsoftheplant,butastheplantmaturesandtheleavesbegintodie,theadultsmoveunderthebractsofthesunflowerheadswheretheycanbeobservedfeedinguntiltheplantsareharvested.
22|Insects
The Sunflower Production Guide
Insects|23
ThesetwospeciesarehighlysuspectedinvectoringPhomablackstem,adiseaseinsunflowerfields.Theonlyspeciesofstemweevillarvathathasbeenfoundtocauseseriousstalkbreakageisthespottedstemweevil.Whenlarvalinfestationsofthisspeciesreach25to30ormoreperstalk,considerableweakeningofstemtissuecanresult,especiallywhentheselarvaebegintocreatetheiroverwinteringcellsinthebaseofthesunflowerstalks.Breakageismostlikelytooccurwhenplantsareunderdroughtstressand/orduringperiodsofhighwind.Thebreakagetypicallyoccursatorslightlyabovethesoilsurfaceincontrasttobreakageattributedtostalkdisease,whichnormallyoccursfartherupthestalks.
Scouting Techniques
LookforstemweevilswhenscoutingsunflowerfieldsinlateJuneandveryearlyJulyusingtheXpatternandexamining5plantsperstopforatotalof25plantsatthe8to14leafstage.Samplingsitesshouldbe75to100feetinfromthefieldmargins.Theaveragenumberofweevilsperplantcanthenbecalculated.
Whensurveyingforstemweevils,moveslowlytoavoidhavingtheadultstemweevilsdroptothesoiland‘playdead’.Adultfeedingbybothstemweevilspeciesisconsideredtocauseinsignificantmechanicalinjury.
Economic Thresholds
Theeconomicthresholdforthespottedsunflowerstemweevilisoneadultperthreeplants.
Figure 14. Adult Apion black sunflower stem weevil (NDSU).
14CONTROL TIPS NoinsecticidesarecurrentlyregisteredforcontrolofsunflowerstemweevilsinManitoba.DelayedplantingofsunfloweruntillateMayorearlyJunehasbeeneffectiveinreducingdensitiesoflarvaeinthestem.Falltillagepracticeswhicheitherburyorbreakupsunflowerstalkswillhelpincreasewintermortalityofstemweevillarvae.Naturalenemiesofthestemweevilincludethreespeciesoflarvalparasitoidsandoneeggparasitoid.Thesewaspshaveaccountedforapproximately30percentmortalityofthestemweevilsinthepast.
The Sunflower Production Guide
Sunflower Maggots
Therearethreemainspeciesthathavelarvalfeedingstagesthatcancauseseedsterilityorstalkbreakageunderhighpopulations.Damageisusuallynegligible.
Biology
Theadultformsofallthreesunflowermaggots(flies)havewingswithadistinctbrownoryellowish-brownpattern.Whileallthreeflyspeciesaresimilarinappearance,theydohavedistinguishingdifferences.
Sunflower receptacle maggot (Gymnocarena diffusa)
Thisspeciesisthelargestofthethreewithabodyabout10mm(0.4inches)longandawingspanofapproximately19mm(0.75inches).Theeyesofthisspeciesarebrightgreenandthewingshaveayellowish-brownandsomewhatmottledappearance.Sunflowerreceptaclemaggotlarvaeattainalengthofnearly8mm(0.31inches)atmaturity.Thelarvae(Figure15)taperfromthefronttotherearandareyellowish-whiteincolor.
AdultsofthesunflowerreceptaclemaggotemergeinlateJunetoearlyJulyaftersunflowerbudsreach5to10cm(2to4inches)indiameter.Eggsarelaidonthebractsofthedevelopingsunflowerheads.Egglayingoccursfrommid-JulythroughAugust.Thehatchedlarvaetunnelintothespongytissueofthereceptacle.Damagetotheheadisnegligible.After30days,thematurelarvaecutasmallemergenceholeontheundersideofthereceptacleanddropintothesoiltopupate.Overwinteringpupaearefoundabout19cm(7.5inches)deepinthesoilbyAugustorearlySeptember.Somelarvaewillpupateinthesunflowerhead.ThereisonlyonegenerationperyearinManitoba.
Sunflower maggot (Strauzia longipennis)
Adults(Figure16)ofthisspecieshaveawingspreadofabout13mm(0.5inches)andabody6mm(0.25inches)long.ThewingsbearbroaddarkbandsthatformafairlydistinctF-shapedmarknearthetips.Thelarvae(Figure15)ofsunflowermaggotarecreamywhite,headlessandlegless,asaretheothertwospecies.Theytaperslightlyatbothendsandattainalengthofabout7mm(0.28inches)atmaturity.
Sunflowermaggotshaveonegenerationperyear.Thisinsectoverwintersaslarvaeinplantdebrisinthesoil.PupationandadultemergencearecompletedinearlyJune.Femaleslayeggsinstemtissueofyoungsunflower,andlarvaefeedinthepithtissueformuchofthegrowingseason.
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15
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The Sunflower Production Guide
Sunflower seed maggot (Neotephritis finalis)
Thissunflowermaggotisthesmallestofthethreespecieswiththeadulthavingabodylengthofabout6mm(0.25inches)andawingspanofapproximately7mm(0.28inches).Thewingshaveabrownlace-likeappearance.N. finalis larvaeattainalengthof4.5mm(0.19inches)atmaturity.
Unliketheothertwospeciesofsunflowermaggots,sunflowerseedmaggotscompletetwogenerationsperyear.Thefirstgenerationpupatesinthehead;thesecondgenerationoverwintersinthesoilaspupae.
Scouting Techniques
Scoutingtechniqueshavenotbeendevelopedforsunflowermaggotsbecausetheycausenegligibledamage.
Economic Threshold – Noneestablished.
Insects|25
CONTROL TIPS Insecticideshavenotbeenwarrantedforcontrolofthispest.
Figure 15. Sunflower maggot larva
Figure 16. Adult sunflower maggot
Figure 17. Sunflower maggot larval feeding causes deformations of the head.
The Sunflower Production Guide
INSECTS ON THE HEADSSunflower Midge
Midgelarvaecanaffectthegrowthofsunflowerheads.Heavily-damagedheadsbecomegnarledandcuppedinwardly,producingfewseeds.
Host Crops
Sunflowers
Biology
Thetiny,tan-colored,adultsunflowermidge(Contarinia schulzi)areonlyabout2mm(1/8inch)longwithawingspanofabout4mm(0.07inch).Thewingsaretransparentandvoidofmarkingsexceptfortheveins.Thefirstpeakoffirst-generationadultemergenceoccursinearly-tomid-July.Asecondpeakoccursabout7to10dayslater.Theadultsprefertolaytheireggsonsunflowerbudswithadiametergreaterthan1inch.Eggsarelaidindividuallyoringroupsindepressionsbetweenthebractsofthesunflowerbud.Themidgelarvaaretiny,beingonly3 mm(1/8inch)longwhenfull-grownandcreamtoyellowishorange.Thenewlyemergedlarvaemovetothebaseofdevelopingseedsorbracts.Presenceofthelarvaeisfrequentlydeterminedbynecroticareasatthebaseof,orbetween,bracts(Figure18).Theyusetheirraspingmouthpartstofeedontheplanttissuesintheselocations.Maturelarvaedropfromtheheadandburrowintothesoil.Ifconditionsarefavorable,theypupateandemergethesameseason.Otherwise,theyremaininthesoilandoverwinteraslarvaeincocoonsor,insomecases,aspupae.Thesecondgenerationadultslaytheireggsamongtheseeds.Usually,thelarvaepupateinthespring.TheadultsstarttoemergeinlateJune.Theadultmidgeonlylivefortwotothreedaysandaredifficulttofindinthefield.
Scouting Techniques
Althoughdamagemaybesevere,itisusuallysporadicandlocalized.Damagetoheadsisusuallyrestrictedtofieldmarginsbut,insevereinfestations,damageispresentthroughoutthefield.Whenmonitoringsunflowerheads,lookformidgelarvaeintheflowerhead,scarredbracts,andtwistedorgnarledflowers.Thelarvaemaybefoundatthebaseofthebractsorfeedinginthefloweratthebaseoftheflorets.A10xmagnifierhelpsinlocatingthetinylarvae.
Economic Threshold
Nothresholdhasbeenestablishedforthispestineitheroiltypeorconfection sunflowers.
26|Insects
19
18
The Sunflower Production Guide
CONTROL TIPS Delayedplanting(untillateMay)mayavoidthefirstmajoremergenceoftheoverwinteringpopulation.However,laterinfestationscanstillbesevere.
Somecommercialhybridsaretoleranttosunflowermidge.Consultyourlocalseeddealerforinformationonthemostresistantvarieties.
Insecticidesdonotworkwellagainstthispest.Theyprovideinconsistentandinadequatecontroloftheadultsandlarvae.Becausethelarvaecrawlintothebudsoonafterhatching,theyareprotectedfromfoliarapplications.Insecticidescancontrolthesunflowermidgeonlyiftheyareappliedtothefoliagejustbeforetheadultsemerge.However,becausethisemergencecannotbeaccuratelypredicted,insecticideapplicationsareineffective.
Figure 18. Larvae feeding causes brown necrotic spots at the base of the bracts.
Figure 19. Severe midge damage causes over growth of the sunflower head.
Insects|27
The Sunflower Production Guide
Sunflower Seed Weevils
Larvaefeedonkernels,causingreducedseedweightandoilcontent.Oftenthekernelsareonlypartiallyfedupon,makingitdifficulttoseparatehealthyfromweevil-damagedseed.Thiscausesdowngradingofconfectionarysunflowerseed.
Host Crops
Sunflowers
Biology
TherearetwospeciesofSeedWeevilsthatcancausedamageinsunflowersinCanada;theredsunflowerseedweevil(Smicronyx fulvus)andthegraysunflowerseedweevil(Smicronyx sordidus).TheredsunflowerseedweevilisthemostcommonofthetwospeciesonthePrairies.Theadults(Figure20)are2.5to3.06mm(1/10to1/8inch),longandarecoveredwithreddish-orange,ovalscales.TheadultsappearduringlateJuneonvolunteersunflowersandfeedonthebractswheretheyformpinpointholes.Asthebuddevelopsandopens,adultsmovetotheinflorescenceandfeedonpollenproducedbythediskflowers.Femaleslaytheireggsinsidetheseedcoatofdevelopingseeds.Populationsarehighestonplantsat50%flowering.Theegglayingpatternfollowsseedfillingwhichprogressesfromtheoutsidetothecenterofthehead.Usually,aninfestedseedcontainsasinglelarva.Thelarvaearesmall,creamcolored,leglessandC-shaped.InlateAugust,thematurelarvaechewanexitholeintheseed,droptothegrounddirectlybeneaththesunflowerhead,andoverwinterinthesoil.
Thegraysunflowerseedweevilisnotascommonandisslightlylarger(3to3.5 mmor1/8inchlong)thantheredseedweevillarvae.Seedsinfestedbythelarvaeenlarge,protrudingabovethesurroundingseeds,andlackakernel.Thedamagecausedbyasinglelarvaofthisspeciesexceedsthatoftheredseedweevilbecauseofthelossoftheentirekernel.However,itusuallydoesnotcauseeconomicdamagetosunflowersusedforoilbecauseofitslowpopulationlevelandlowreproductiverate.
May June July August September
Larvae overwinter in soil
Larvae pupate, new adults feed on volunteer sunflowers
Females lay eggs in developing seeds, eggs hatch
Larval feeding, larvae move into soil
Larvae overwinter in soil
28|Insects
CONTROL TIPS
The Sunflower Production Guide
Scouting Techniques
Beginscoutingforseedweevilsassoonastheyellowraypetalsappear.Continuecountsuntiltheeconomicthresholdlevelhasbeenreachedormostplantshavereached70%pollenshedatwhichtimeveryfewseedsaresuitableforegglaying.
Whensampling,followanXorZpatterninthefield.Initiatecountsmorethan100feetintothefieldascountstakenalongthefieldmarginwillleadtoabnormallyhighweevilcountsthatwillnotberepresentativeofthefield.Countthenumberofweevilson5plantsateachsiteforatotalof25plants.BrushthefaceoftheheadsvigorouslytobringtheweevilstothesurfaceorspraymosquitorepellentcontainingDEETonthehead.Thiswillforcetheweevilstomoveoutoftheirhidingspots.Careshouldbetakentonotconfuseotherinsectswhichmaybepresentonsunflowerheads,suchasminutepiratebugs(Figure21)forseedweevils.
Economic Thresholds
Inoilseedsunflowers,thethresholdis10to12weevilsperplant.Inconfectionsunflowersthethresholdis1to2weevilsperplant.
Figure 20. Adult Red Sunflower Seed Weevil
Figure 21. Sunflower seed weevils on top and the much smaller minute pirate bug nymphs below.
Insects|29
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21
Earlyplantinghelpsreduceseeddamage.Whenplantedearly,thesunflowersarecompletedanthesis(flowering)beforepeakweevilpopulationsandarenolongersusceptibletoegglaying.
Insecticides,sometimesincombinationwithtrapcropping,remainsthemajormanagementtool.Determinetheaveragesunflowerplantgrowthstagebeforeapplyinganinsecticide.TheweevildoesnotbegintolayeggsonsunflowerheadsbeforeR5.4(theouter40%offloretshaveopened).Iftreatmentisnecessary,insecticidesshouldbeappliedbeforethreeoutoftenplantsreach40%bloom.
The Sunflower Production Guide
Banded Sunflower Moth
Larvaefeedonsunflowerfloretsandseeds.
Host Crops
Commercialsunflowers.Severalspeciesofwildsunflowersarealsoknownhostsofbandedsunflowermoth.
Biology
Thebandedsunflowermoth(Cochylis hospes)isasmall,straw-coloredmothabout7mm(0.3inch)long(Figure22)withabrowntriangularareainthemiddleportionofthefrontwings.Newlyhatchedlarvaeareoff-whitewithadark-brownheadcapsuleandabout1.5mm(0.06inch)long.Asthelarvaegrow,thereisagradualcolorchangetolightpinkoryellow,thentoreddishorpurplishandfinallytogreenatmaturity(Figure23).Full-grownlarvaeareabout10mm(0.4inch)long.
Theadultmothsstartemergingfromthesoilinmid-Julyandarepresentthroughtomid-August.Mothsflyfromlastyear’ssunflowerfieldstothecurrentyear’ssunflowerfields.Adultmothsrestinvegetationalongfieldmarginsduringthedayandmoveintothefieldtolayeggsattwilight.Theylayeggsonthebractsofsunflowerheads.Eggshatchin5to8days.Larvaecanbepresentinsunflowerheadsfromaboutmid-Julytomid-September.Maturelarvaedroptothegroundandspincocoonsinthesoilwherewinterispassed.PupationtakesplaceinlateJuneorearlyJulythefollowingyear.
Newlyhatchedlarvaemovefromthebractstothefloretsofthesunflowerhead,wheretheyenteropenfloretstofeed.Ifeggshatchpriortotheopeningoftheflorets,larvaewillfeedonbracttissuebeforemovingtotheflorets.Larvaecontinuetofeedinthefloretsuntilthethirdinstar,reducingthetotalnumberofmatureseedsproduced.Duringlaterstagesofdevelopment,thelarvaetunnelthroughdevelopingseeds,usuallyenteringatthetopandleavingafterthecontentsareeaten.Eachlarvamaydestroy6to7matureseedsinadditiontothefloretseatenbytheearlierinstarlarvae.Sincetheseedkernelisentirelyconsumedbythelarva,theseedwillnormallypassthroughthecombine.
Thegreatestdamagebybandedsunflowermothlarvaehasbeenshowntooccurattheedgeofthefield.
Scouting Techniques
Fieldsshouldbemonitoredwhenplantsareinthelatebud(R-4)toearlybloomstage(R-5.1)ofdevelopment.
Monitorforadultmothsinearlyeveningorearlymorningwhenthemothsaremostactive.Samplingsitesshouldbeatleast75to100feet(23to30m)fromthefieldmargin.Countmothson20plantsfrom5differentsitesforatotalof100plants.
30|Insects
CONTROL TIPS Iftreatmentiswarranted,itshouldbeappliedattheR5.1sunflowerplantgrowthstage.Insecticidesshouldbeappliedearlyinthemorningorlateinthedaytominimizetheadverseeffectonbeesandotherpollinators.Parasiticwaspsattackboththeeggsandlarvaeandgeneral
predatorsinthesunflowerfieldalsoconsumebothlarvaeandeggs.Minutepiratebugsfeedontheeggsandyounglarvae.Groundbeetlescandestroyabout40%ofoverwinteringlarvaeandpupae.Atleast4differentspeciesofparasitesattackthelarvaeofthebandedsunflowermoth.
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Figure 22. Banded sunflower moth adults are characterized by the dark band along the middle of the back.
Figure 23. Larva go through 5 instars and feed on the developing kernel within the seed.
Figure 24. Banded sunflower moth larva create a webbing on the face of sunflower heads.
The Sunflower Production Guide
Samplingstrategiesbasedonscoutingforadultmothsduringdaylighthoursandforeggshavealsobeendeveloped.
Economic Threshold
Ifmonitoringintheearlyeveningorearlymorning,onebandedsunflowermothpertwoplantsisareasonableeconomicthreshold.
NOTE:TheArthur’ssunflowermoth(Cochylis arthuri)isverysimilartothebandedsunflowermoth.TheArthur’ssunflowermothlarvaealsofedondevelopingseedsinthesunflowerheadcausingsimilardamagetothatofthebandedsunflowermoth.Theadultsalsohavedarkbandingacrossthewings,althoughtheycanbedistinguishedfrombandedsunflowermoth.Younglarvaearecreamcolored,mid-instarlarvaearelighttodarkpink,andlast-(fifth-)instarlarvaearelighttodarkgreen.
Insects|31
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32|Insects
Lygus Bug
Feedingbylygusbugsondevelopingseedscancausekernelbrownspot,smallbrowntoblackspotsonthebluntordistalendofsunflowerseeds.
Host Crops
Lygusbugshavebeenrecordedonover385cropandweedspecies.
Biology
Adultlygusbugs(Figure25)areabout5mm(0.2inch)longand2.5mm(0.1 inch)wide.Theyvaryincolorfrompalegreentoreddish-brownandhaveadistincttriangleor“V”markonthewings.Firststagenymphsareverysmall,winglessandbrightgreen.Nymphs(Figure26)maylooksimilartoaphidsbutaremuchmoremobile.
Lygusbugsfeedonplantsbyinjectingplanttissuewithdigestiveenzymes,andthenextractingnutrientswiththeirneedle-likemouthparts.Lygusbugfeedingondevelopingsunflowerseedscancausescarringontheseeds,knownaskernelbrownspot.Whilebrownspotisnotknowntoaffectyield,thisqualityissuecanbesignificantinconfectionsunflowersbecauseprocessorsareonlyallowed0.5%damageinthefinishedproduct.Lygusbugfeedingcanalsoresultinabittertastetotheseeds.Whilebrownspotisvisibleondehulledkernels,thereisusuallynosignontheexteriorofthehullthatthekernelhasbrownspot.
Lygusbugsaremobileandcanbefoundonmanycrops.Lygusbugsprobablymovetosunflowersfromalfalfa,canolaorotherhostcropswhenthosecropshaveeitherbeenharvestedorsenesced.
Scouting Techniques
Scoutforadultsornymphsonthesunflowerheadsorfoliage.
Economic Thresholds
Lygusbugsarecapableofdamaging30to35seedsperheadperadult.Withtheindustrystandardallowingforamaximumof0.5%kernelbrownspot,theeconomicthresholdforlygusbugsonsunflowersislikelyabout1lygusbugper9heads.
Inresearchtrials,damagetosunflowerheadswasapproximatelytwiceasseverewheninfestationsoccurredatlatebudandearlybloomcomparedtostageswhenheadshadcompletedflowering.Thus,lygusbugmanagementshouldbeinitiatedpriortooratthebeginningoffloweringifadultdensitiesapproachtheeconomicthreshold.Fieldsshouldbemonitoredforlygusbugsuntilfloweringiscompletedtoreduceincidenceofkernelbrownspotdamageto confectionsunflowers.
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CONTROL TIPS
InsecticideapplicationismostbeneficialwhenappliedduringearlyfloweringattheR5.1stage.AsecondapplicationmaybewarrantedifLygusbugpopulationsarehighinneighboringfields,andpopulationsareexpectedtomigratetothesunflowerfield.ConsultthecurrentGuidetoCropProtectionforregisteredinsecticides.
Figure 25. Adult lygus bugs are characterized by a triangle across the wings.
Figure 26. Lygus bug nymphs resemble the adults but lack wings.
Insects|33
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BENEFICIAL INSECTS
34|Insects
Minute Pirate Bug
Bothnymphsandadultsfeedonavarietyofsunflowerpestsincludingaphidsandtheeggsandlarvaeofbandedsunflowermoth.
Green Lacewing
Adultsfeedonaphidhoneydew,plantpollenandplantnectar.
Green Lacewing Larvae
Predatortoavarietyofsunflowerpestsincludingaphids,sunflowerbeetleeggsandlarvae,andbandedsunflowermotheggsandlarvae.
Lady Beetles
Consumesunflowerbeetleeggs,aphids,andbandedsunflowermotheggsandlarvae.
Lady Beetles Larvae Damsel Bugs
Preyonsunflowerbeetlelarvae,andbandedsunflowermotheggsandlarvae.
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Insects|35
Two-Spotted Stink Bug
Preyonsunflowerbeetlelarvae.
Parasitic Wasps
Attackboththeeggsandyounglarvae ofbandedsunflowermoth,sunflowerseedweevilsandsunflowerstemweevils.
Ground Beetles (Carabid Beetles)
Candestroy40percentofoverwinteringlarvaeandpupaeofsunflowerbeetles.
Hover Fly
Increasescropyieldbyenhancingpollination.Feedson aphids.
Honey Bee
Increaseyieldinsunflowerbyenhancingpollination.
The Sunflower Production Guide
Pollination
Unlikenativesunflowers,currenthybridshavebeenselectedforandpossesshighlevelsofself-compatibility.Althoughself-compatiblesunflowerhybridsusuallyout-produceself-incompatiblecultivars,modernhybridscontinuetobenefitfrominsectpollination.Studieshaveshownthatinmostsunflowerhybridsseedset,yieldandoilquantityisincreasedwhenpollinators(suchasbees)arepresent.
Toachievemaximumyieldsandquality,oftentheuseofinsecticideisrequiredtoprotectthecropfrominsectcompetitors.Unfortunately,manyofthemajorinsectpestsofsunflowerattackthecropduringfloweringandinsecticideapplicationsharmthepollinatingbees.Belowaresomekeystrategiesthatcanhelpprotectthepollinators.
Key strategies:
� Scoutfieldsandapplyinsecticideonlywhenneeded.� ApplyInsecticideintheevening-Honeybeesareforagingwhenthesunis
upandduringthewarmerpartsofthedayandreturntothehiveatnight.Whenthebeesreturntothefieldthenextday,theeffectonthebeeswillbesignificantlyreduced.
� Lessharmfultobeesdoesnotnecessarilymeanlessharmfultopests–Thisisduetotherepellenteffectonbeesfromtheresidueofsomeinsecticides.Selectinsecticidesthatprovideeffectivecontrolofthetargetedpestswhileminimizingimpactonbees.
� Communicatewithbeekeepers–Contactingthebeekeeperaboutaninsecticideapplication,theinsecticidechosen,andthestepstakentoreduceharmtopollinators,helpsthebeekeepertodecideifadditionalmeasuresshouldbetakentominimizebeedamage.
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The Sunflower Production Guide
DISEASESEARLY SEASON DISEASESDowny Mildew
Downymildewiscapableofkillingorstuntingplants,reducingstandsandcausingsevereyieldlossesduringwetyears.
Host Crops
Sunflower
Biology
Downymildewiscausedbyasoil-borne,wind-borneandseed-bornefungiPlasmopara halstedii,whichcansurviveforupto10yearsinsoil.Undercool,water-saturatedsoilconditions,thesporesgerminateuponcontactwithsunflowerroots,enter,andspreadthroughouttheentireplant.Thisissystemicinfection.Systemicinfectionoccursonlywhentherootsarelessthan2incheslongwhentheycontactthefungi.Sunflowerplantssurvivingtheinitialinfectionwillproducewhitesporesontheundersideofcholoroticareasonleaves.Thewhitesporesareair-borne,anduponlandingonsunflowerleavesmaycausesecondaryinfections.Secondaryinfectionsaremostcommonwhensunflowerleavesremainwetforprolongedperiodsoftime.Plantsaresusceptibletosecondaryinfectionsforamuchlongerperiodoftimeversussystemicinfectionsviarootinfection.Asinfectedplantsrotandaretilledintothesoil,thefungusformstherestingstagewhichwillgerminateduringfavorableconditionsinsubsequentyears.
Figure 38. Seedling Sunflower with downy mildew.
Figure 39. Downy Mildew causes stunting and heads to face straight upwards.
Diseases|37
The Sunflower Production Guide
Symptoms
Symptomscanvaryconsiderablydependingonamountofinoculum,theageandhostorganattackedandenvironmentalfactors.Symptomscanbebroadlyclassifiedasthosecausedbysystemicorlocalizedinfections.Rootinfectionofseedlingsoryoungplantsresultsinsystemicinfection.Severelyinfectedplantsmaydiebeforeorshortlyafteremergenceorintheseedlingstage.Typicalsystemicsymptoms(Figure38)inseedlingsincludedwarfing,yellowingoftheleavesandtheappearanceofwhite,cottonymassesonthelowerandsometimesupperleafsurfaceduringperiodsofhighhumidity.Whenseedlingsareinfectedseveralweeksafteremergence,orafungicideseedtreatmentinhibitsratherthanpreventsinfection,theplantsstartshowingsymptomsatthefour-,six-,oreight-leafstage;thisistermed‘delayedsystemicinfection’.Theseplantsmayormaynotdeveloptypicaldownymildewleafsymptoms,butaretypicallystuntedwiththickened,clublikeroots.Theheadsofthefewplantsreachingmaturityfacestraightupwardsandseldomproduceviableseed(Figure39).Airbornedownymildewsporescancauselocalizedsmall,angularfoliarlesionswiththewhitefungalgrowthontheundersideoftheleaf.Theseinfectionsgenerallyhaveminimalimpactonyield.
Yieldlossesmaybesubstantial.Ifinfectedplantsaredispersedrandomlythroughoutthefield,yieldlossesprobablywillnotbeobservedunlessinfectionexceeds15percent.Neighboringplantscancompensateforseverelyinfectedplantsbygrowinglargerheads.Whenthediseaseisinalocalizedarea,suchasalowspotinafieldandallplantsareinfected,yieldlosscanbesubstantial.
Scouting Techniques
Infectedplantscanmostoftenbefoundaloneorinstandingwater.
38|Diseases
CONTROL TIPS
Resistantvarietiesareavailable;however,duetothedevelopmentofnewraces,resistancemaynotbeasufficientmanagementtoolinallfields.Fungicideseedtreatmentscanbeaneffectivemanagementtoolfordownymildew,butaswithgeneticresistance,thepathogenhasdevelopedresistancetometalaxylandmefanoxam,twoofthemostcommonlyusedfungicides.Otherseedtreatmentoptionsareavailableandmorewillbelabeledinthefuture.RefertothecurrentissueoftheGuidetoCropProtectionforupdatedinformationonproductsandratesforapplication.Othermanagementproceduresaretocontrolweedhostswhichincludewildandvolunteersunflowerstohelpreduceinoculum.
The Sunflower Production Guide
FOLIAR DISEASESRust
Earlyinfectionofsusceptiblevarietiescandecreaseheadsize,seedsize,oilcontentandyield.Confectionhybridsaremoresusceptiblethanoil-seedtypes.
Hosts
Wildsunflowerandcultivatedsunflower
Biology
SunflowerrustiscausedbyPuccinia helianthi.Infectioncanoccuratanytimeduringthegrowingseason,dependingontheinoculumsourceandenvironmentalconditions.Conditionsfavorableforinfectionarefreewaterontheleaves,eitherfromrainfallordew,andwarmtemperatures.Aminimumoftwohoursofwetleavesissufficientforrustinfection;sixtoeighthoursofleafwetnessresultsinthemaximumamountofinfection.Sunflowerrustsporesoverwinteronthedebrisfrominfectedsunflowerleavesandstemsofpreviouscrops.Inthespringsporesgerminatetoinfectvolunteerseedlings,wildsunflowerornewyoungplantsinnearbyfields.Underfavorableconditions,sporeproductionandinfectioncanoccurcontinuouslywithinayear.The‘repeatingstage’isthemostdamaging,asmultiplewavesofsporesarespreadbywindtootherfieldsasconditionsallow.Asthecropripens,thesporesformtheoverwinteringstagewhichcanthenre-infectfollowingsunflowercrops.
Symptoms
Thefirstsignsofrustusuallyappearwhensunflowersareatorpastbloomasenvironmentalconditionswithinthecropcanopyaremorefavorableforinfection.Theaecialstage(Figure41)ofrustappearslatespringtosummerasclustersoforangecups.Themostcommonstageofrust(uredinia)(Figure 42)isoftenobservedwithintwoweeksoftheaecia.Thesepustulesaresmall(0.1to1mm),cinnamon-brown,canberubbedofeasilyandoccuronboththeupperandundersidesofleaves.Asthediseaseprogresses,urediniamaybefoundontheupperleaves,stemandbractsofthesunflowerplant.Inresponsetotemperature,theurediniaconverttotelia(blackspotsontheuppersurfaceofleaves)attheendoftheseasonwhichdonotruboffandaretheoverwinteringstructures.
Economic Threshold
Rustseverityontheupperfourleavesis3percentorgreater.
Diseases|39
0.5% Leaf Area Infected 1% Leaf Area Infected 2% Leaf Area Infected 5% Leaf Area Infected
Figure 40. Leaf area infected by rust.
42
CONTROL TIPS
Themosteffectivewaytoavoidlossfromrustisbyplantingrust-resistanthybrids.Mostoilseedandconfectionaryhybridshavegoodtoexcellentresistancetomostracesofrust.Rotationtoothercropsisalsoausefultooltominimizeinfections,assunflowerrustonlyinfectssunflowers.Ifpossible,avoidplantingnexttoafieldthathadsunflowerslastyear;managewildsunflowersorvolunteersunflowersastheyarehostsforthedisease.Earlyseedingandshortseasonhybridscanalsohelpminimizediseaseseverity.Anyculturalpracticewhichfostersadensecanopy,suchashighplantstandsandhighnitrogenfertilization,whichtrapsdew,increaseschancesofasevererustinfectionandshouldbeavoidedifrisksarehigh.Foliarfungicidesareregisteredforrust.ConsultthecurrenteditionofGuidetoCropProtectionfor products.
Figure 41. Aecia cups on the underside of sunflower leaf.
Figure 42. Rust uredinia develop on the under-and upper-leaf surfaces.
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The Sunflower Production Guide
40|Diseases
The Sunflower Production Guide
Alternaria Leaf and Stem Spot
Alternarialeafspotisaubiquitousdiseaseonsenescingleavesandgenerallyoflittleconcern.Underwarmandhumidconditions,itcanhoweverbecomeaseriousdefoliatingandyieldreducingdisease.
Host Crops
Sunflower,safflowerandcocklebur
Biology
Alternariafungioverwinterondiseasedstalksandmaybeseed-borneatlowlevels.SeedlingblightscausedbyAlternariamaydevelopwhensunflowerplantsemergeinrainyweatherinAlternaria-infestedsoil.Alternariasporesarespreadbywindandsplashingwater.Thefungirequirefreewaterfor4hoursforinfectiontooccur.Leafsymptomsaremostfrequentlyobservedafterfloweringasthedensecanopyisconducivetoinfection.Onceestablished,thediseasecandevelopquicklyunderfavorableconditions.InwesternCanada,climateisnottypicallyconduciveforAlternariaepidemicsandgenerallyonlythelowersenescingleavesareaffected.
Symptoms
Darkbrownirregularspotswithdarkbrowntopurplebordersandagraycenterdeveloponleaves(Figure43).Thespotsonyoungplantsmayhaveayellowhalo.Leaflesionsmaycoalesce,causingleavestowither.Stemlesionsbeginasdarkflecksthenenlargetoformlong,narrowlesions.Thestemlesionsoftenjointoformlargeblackenedareaswhichmayresultinstembreakage.Thelesionsarelocatedrandomlyalongthestemandnotassociatedwithapetiole.
43
CONTROL TIPS
Croprotationandburyinginfestedcropresidueto hastendecompositionhelpsminimizeAlternaria infection.
Figure 43. Alternaria leaf lesions close up.
Diseases|41
The Sunflower Production Guide
Septoria Leaf Spot
Septoriaiswidelydistributedonsunflowersbutusuallycauseslittledamage.Insevereinstancesitcancausedefoliationofthelowerleaves.
Host Crops
CultivatedandWildSunflower
Biology
SeptoriaiscausedbythefungiSeptoria helianthi.Thefungisurviveoninfectedcropresidueandcanalsobeseed-borne.Thediseasecanappearanytimeduringthegrowingseasonwithinitiationfavoredbymoderatelyhightemperaturesandabundantrainfall.
Symptoms
Septoriadevelopsfirstonthelowerleavesandspreadsupwardsthroughthecanopy.Thelesions(upto15mmindiameter)beginaswater-soakedareaswhicharegreasygreeninappearance.Thespotsbecomeangulartodiamondshaped,withtancentersandbrownmargins.Youngspotsareoftensurroundedbyanarrowhalothatgraduallymergeswiththesurroundinggreentissue(Figure44).Maturespotscontainsmallblackspecksorfruitingbodies.ThisisthebestwaytodistinguishAlternariafromSeptoria.Thelesionsmaycoalesceinlaterstagesandtheleafmaywitheranddie.
42|Diseases
44 CONTROL TIPS
Croprotation,incorporationofsunflowerresidueanduseofcleanseedarethebestmanagementpracticestomanageSeptoria.
Figure 44. Septoria lesions contain small black fruit bodies.
STALK AND ROOT-INFECTING DISEASESSclerotinia Wilt and Basal Rot
Infectedplantsdierapidly,andiftheplantdiespriortoseedmaturityitresultsinyieldloss,lowertestweight,andloweroilcontent.
Host Crops
Sclerotiniahasaverywidehostrangeofover360species,whichincludessunflowers,canola,mustard,drybeans,fieldpeas,lentilsandpotatoes.
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The Sunflower Production Guide
CONTROL TIPS
Managementofsclerotiniaisdifficultbecauseofthewidehostrange,butrotationtocerealsandcornisthemosteffectivetominimizesclerotiniainthesoil.Sunflowerhybridswithsomelevelsofresistanceareavailable.TheuseofamycoparasiteswhichfeeduponotherfungihasshowntoattackSclerotinia.OnecommerciallyavailableisConiothryium minitans(Contans).Thismycoparasitecankillsclerotiainseveralmonthsratherthanyears.
Figure 45. Sclerotinia wilt.
Figure 46. Sclerotinia Basal rot lesion.
Biology
SclerotiniaoverwintersasSclerotinia sclerotioruminthesoiloronplantdebris.Sclerotiaareirregularlyshapedstructureswhichrangeinsizeandshapefromsphericaland1/8inchindiametertoY-shapedandupto1inchinlength.Thesclerotiabodiescansurviveinthesoilfor5ormoreyears.Assunflowerrootsgrownearsclerotiniainthesoil,thesclerotiaarestimulatedtogerminateproducingmyceliumwhichinfectsthelateralroots.Sclerotiaforminthedecayedstempithandontherootsastheplantdies.Thesclerotiaarereturnedtothesoilduringtillageoperationsandserveassourcesofinoculumforthenextsusceptiblecrop.
Soilmoistureandtemperatureduringthegrowingseasonarenotcriticalfactorsaffectingtherateofincidenceofsclerotiniawilt.
Symptoms
Wilt(Figure45)canappearatanytimebetweenemergenceandmaturity,butismoreprevalentaroundflowering.Suddenwiltoftheplantoccurswheninfectedrootscannotuptakeadequatewatertomeetthedemandsoftheplant.Examinationofthestem-rootareawillrevealatan-brown,watersoakedlesionatthesoilsurface(Figure46).Thestalksandrootsmaybecomecoveredwithwhitemyceliaandhardsclerotiabodiesdevelopunderverywetsoilconditions.
Diseases|43
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The Sunflower Production Guide
Sclerotinia Mid-Stalk Rot
Mid-stalkrotisthediseaseleastoftencausedbySclerotinia.Lodgingcancausecompleteyieldlossonaperplantbasis.
Biology
Underwetsoilconditions,thesclerotiainthesoilcangerminatetoformsmallmushroomscalledapotheciathatproduceair-bornespores.Thesporescanoriginateinthesunflowerfieldorcanbeblowninfromadjacentfields.Sporescanmovebyrainsplash,variousinsectcarriersandupto1kmbyair.Thesporesrequirefreewaterandsenescingplanttissuetogerminateandinfectplants.Mid-stalkinfectionmayresultfromleafinfectionorinfectionattheleafaxil.
Symptoms
Infectioncanoccuranytimefromseedlingtomaturitydependingonthepresenceofinfectingsporesandfavorableenvironmentalconditions.Mid-stalkrotbeginswithinfectionoftheleaf,andthefungusprogressesinternallythroughthepetioleuntilitreachesthestem.Theleaflesionsarenotuniqueenoughtoidentifythefungus,butthestemlesionsareidenticaltothatformedbyrootinfection;tancoloredandwater-soaked(Figure47).Thesclerotiacandevelopwithinthestemorontheexteriorofthestem.Leavesabovethelesionwilt,andthestalkeventuallydisintegratesbecomingshreddedasonlyvascularcomponentsofthestemremain(Figure48).
CONTROL TIPS
ThecommentsmadeaboutSclerotiniawiltalsoapplytomid-stalkrotmanagement.Culturalpracticestoavoidhighplantdensitiesbyreducingpopulationsandhighnitrogenfertilizationhelplowertheincidenceofinfection.Shalloworzero-tillagepracticesmayaidinfasterdeteriorationassclerotiaareleftonthegroundsurfaceandsubjecttoincreasedenvironmentaldeterioration.Resistancegeneshavebeenthemosteffectiveapproach,andbreedingforhighertolerancecontinues.
Figure 47. Sclerotinia mid-stalk rot lesion
Figure 48. Sclerotia bodies develop within the stem tissue or on the surface of the stem.
48
44|Diseases
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The Sunflower Production Guide
Phoma Black Stem
PhomaisthemostwidespreadstalkdiseaseinthenorthernGreatPlains,but yieldlossesareconsideredminimal.
Host Crops
Cultivatedsunflower
Biology
Thefungus(Phoma macdonaldii )overwintersininfecteddebris.Phomainfectionoccursthroughoutthegrowingseason;however,itisnotusuallynoticeduntilthestemlesionsbecomeobviouslaterinthesummer.Leavescanbeinfectedbywindcarriedspores,rainsplashedsporesorsporestransmittedbyinsects.Stemweevilsaresuspectedintransmittingthefungiinternallyandexternally.Adultweevilsfeedingontheleavescauseleaflesionswhereascontaminatedlarvaespreadthefungusastheytunnelthroughoutthestem.LeaflesionsarenotdistinctiveandcanbeconfusedforAlternaria.Theleafinfectionsprogressdownthepetioletothestalk.Underfavorableconditions,theleafwilts,thepetioleturnsuniformlyblack,andthestemlesionsexpand.
Symptoms
Large,jetblacklesionsdeveloponthestem(Figure49),sometimesreachingabout4to5cminlength.Thelesionsareuniformlyblackandshinywithdefiniteborders.Smallcircularfruitingbodiesofthefungusareproducedonthesurfaceofthestembuttheserequireahandlenstosee.Thefungusmayalsoproducelesionsonthebackofthehead,ontheleaves,andatthebaseofthestalk.Stemlesionsdonotresultinpithdamageorlodgingandaregenerallyregardedassuperficiallesions.IfstemweevillarvatunnelingspreadsPhomasporeswithinthepith,extensivepithdegenerationcanoccur.
CONTROL TIPS
CulturalpracticestominimizePhomaincludesafouryearrotationtominimizetheinoculumloadinthesoil,delayedplantingandavoidinghighplantpopulationsandhighnitrogenfertilization.Controlofstemweevilscanhelpreducetransmissionofthefungusbutinsecticideapplicationisrarelyeconomicallyjustified.Somehybridsaremoretolerantthanothers,butnoneareimmunetothe disease.
Figure 49. Phoma black stem lesion
Diseases|45
The Sunflower Production Guide
Phomopsis Stem Canker
InrecentyearsPhomopsishasbecomeaveryprevalentdisease.Yieldlossesresultfromsmallerheads,lighterseedandlodgingduetoweakenedstems.
Hosts
Sunflower
Biology
Thefungi(Phomopsis helianthii)overwinteroninfectedplantdebrisandsporesarerainsplashedorwindblownontoleaves.Theinfectioninitiatesatleafmarginsoflowerleaves,developingintoabrownnecroticareaborderedbyachloroticmargin.Theinfectionspreadsdownthroughtheveinstothepetioleandfinallytothestem.ThesymptomsaresimilartothoseofVerticilliumleafmottle;however,withVerticilliumveinsremaingreen.Stemlesionsusuallydonotappearuntilflowering.Thediseaseismostsevereunderconditionsofprolongedhightemperaturesandhighrainfall.
Symptoms
Firstsymptomsinitiateonlowertomiddleleavesafterfloweringasnecroticspotswithachloroticborderonleafmargins.Thestemlesionsbeginasasmallbrownsunkenspotbutenlargesrapidlybecomingalargetantolightbrownlesionorcankercenteredonaleafpetiole.LesionsaremuchlargerthanPhomablackstem,sometimesreaching6inchesandbrownratherthanblack.Blackfruitingbodies(pycnia)formoninfectedtissue.Phomopsiscausesextensivepithdegradationandthestalkcanusuallybecrushedundermoderatethumbpressure.PhomopsisinfectedplantsaremorepronetolodgingthanPhomainfectedplants.
50CONTROL TIPS
Thoroughincorporationofthesunflowerstalksintothesoiltoburyresidueandcroprotationcanreducediseaseincidenceandseverity.CropresidueleftonthesoilsurfacefostersdevelopmentofPhomopsis.HybridsresistanttoPhomopsis,developedusingparentallinesfromEuropewherethediseaseisparticularlysevere,arecommerciallyavailable.
Figure 50. Phomopsis Stem Canker
46|Diseases
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The Sunflower Production Guide
Verticillium Leaf Mottle
Verticilliumcansignificantlyreducesunfloweryieldespeciallyonlightersoils.Qualitymayalsobeaffectedthroughdecreasedoilcontentandseedsize.
Host Crops
Variousplantspeciescanbeinfectedincludingsunflowers,potatoes,alfalfaandsweetclover
Biology
Thefungus(Verticillium dahliae)isseed-andsoil-borne.Itsurvivesasverysmall,black,restingbodies(microsclerotia)indiseasedsunflowerdebrisandbroadleavedweeds,persistingfor5to10years.Themicrosclerotiagerminateinresponsetorootexudates.Theroottipsofsunflowerplantsareinvadedand,eventually,allpartsoftheplantbecomeinfected.Thefungusproducestoxinswhicharetranslocatedthroughouttheplantcausingthechloroticandnecroticareasbetweentheveins.Whentheplantdies,thefungusproducesblackfungalbodiesthatreturntothesoilwiththeplantdebris.
Symptoms
Symptomsusuallyarenotobserveduntilflowering,butmayappearatthesix-leafstageundersevereconditions.Initialsymptomsbeginastinychloroticflecksthatincreaseinsizewithtimedevelopingintoextensiveinter-veinalyellowing(Figure51).Symptomsbeginonthelowerleavesandprogressslowlyuptheplantandmayeventuallyinfectallleaves.Affectedleavesquicklybecomedry.Thevascularsystemmaybediscoloredbrown,apparentasaringaroundthepithincrosssection.Inseverelyinfectedplants,thepithisblackenedwithalayeroftinyblackfruitingbodies.
CONTROL TIPS
Mostoil-seedhybridscontainresistancetoVerticilliumwhereasconfectionhybridsaregenerallymoresusceptible.However,anewstrainhasrecentlybeenidentifiedinCanadaandtheU.S.whichisabletoovercomethesourceofresistanceinthesevarieties.Thediseaseismoresevereonlighterlandwithahistoryofsunflowercroppingthanonheavy,claysoil.Rotationisimportantonlightersoilwithahistoryofsunflowercroppingtoreduceinoculumloadinthe soil.
Figure 51. Verticillium Leaf Mottle
Diseases|47
The Sunflower Production Guide
HEAD ROT AND DISEASES OF MATURE PLANTSSclerotinia Head Rot
Head-rotisconsideredthemostimportantdiseaseaffectingsunflowerproduction,causingyieldandqualityloss.
Hosts
Sunflower,canola,mustard,drybeans,fieldpeas,lentils,potatoes
Biology
Sclerotiniahead-rot(Figure52)isquitevariable,usuallyoccurringlateintheseasonandinfluencedprimarilybytheamountofrainfallfromfloweringthroughtoharvesting.Aswithsclerotiniamidstalkrot,head-rotiscausedbyair-bornesporesproducedbyapothecia(smallmushrooms)eitherwithinthefieldorblownfromaneighboringfield.Thesporesrequirefreewaterandafoodbasesuchasdeadorsenescingplanttissuetogerminateandinfect.Ascosporescolonizethedeadfloretsandpollenonthefaceofthehead.Afterinfectionittakesseveralweeksuntiltheappearanceofbrownlesionsonthebackofthehead.
Symptoms
Thefirstsymptomsofheadrotusuallyaretheappearanceofwater-soakedspotsorbleachedareasonthefleshybackofthehead.Thefunguscandecaytheentirehead,withtheseedlayerfallingawaycompletely,leavingonlyableached,shreddedvascularsysteminterspersedwithlargesclerotia.Thebleached,skeletonizedheadsresemblestrawbroomsandareveryobviousinthefieldevenfromadistance.
Yieldlossfromheadrotonanindividualplantcanrangefromminimaltototallossiftheheaddisintegratesanddropsalltheseedtothegroundpriortoharvest.Intactbutdiseasedheadswillhavelightandfewerseeds,withloweroilcontentandwillshatterduringharvest.
52
48|Diseases
CONTROL TIPS
Sunflowerhybridsexhibitvariablerangeofsusceptibilitytoheadrot,butnohybridsarecommerciallyavailablewithadequateresistance.Fungicidesmayhelpreducetheincidenceofheadrot,withapplicationsmadepreventivelysinceseveralweekslapsefrominfectiontosymptomdevelopment.ConsultthecurrenteditionoftheGuidetoCropProtectionforproductinformation.
Figure 52. Sclerotinia Head Rot
The Sunflower Production Guide
Rhizopus Head Rot
RhizopusisaverywidespreaddiseaseinthecentralGreatPlains.Affectedheadswillhavealightertestweight,loweroilcontentandreducedseedyields.
Host Crops
ManyhostsforRhizopusincludingsunflower,beetsandtobacco
Biology
Susceptibilityoftheheadincreasesfromthebudstageuptothefullbloomandripeningstages.Sporesaredisseminatedbywind,rainandinsects.Rhizopusenterstheheadthroughwoundscausedbyhail,birds,insectsandhasbeenassociatedwithsunflowermidgedamage.Rapiddiseasedevelopmentoccursinwarm,humidweather.Oncetheheadisfullycolonizedandalltissuekilled,theheaddriesupandbecomes‘mummified’.
Symptoms
Initialsymptomsaresimilartootherheadrotdiseases;brown,sunken,watersoakedlesionsonthebackofthehead.Asthelesionsenlarge,theinterioroftheheadbecomesmushy(Figure53).Theinterioroftheheadbecomesfilledbymyceliuminterspersedwithblackfruitingbodiesresemblingpeppergrains.Oncetheheaddriesupitischaracterizedbyadarkbrown,pepperyappearanceoftissuesinthereceptacleandbecomesveryhard.
53
CONTROL TIPS
ControllingheadinsectsisthemostefficientmethodtominimizeincidencesofRhizopusheadrot.Geneticresistancehasbeenidentified,butseverityofthediseasehasnotwarrantedintensiveresearch.RotationdoesnothelpreducetheincidenceofRhizopusduetothenumberofRhizopusspecies.NofungicidesareregisteredforcontrolofRhizopusheadrot.
Figure 53. Rhizopus Head Rot
Diseases|49
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54
BLACKBIRDSSunflowerseedsareparticularlyvulnerabletopredationbyblackbirdsduetothehighnutritionalvalue,easyaccessibility,andheadsservingasaperchduringfeeding.Blackbirdnestsarebuiltindensevegetation,mostoftencattails.Afternesting,blackbirdsformlargeflocksandbeginfeedingingrainfieldsandforthisreason,extensivefeedingdamageoftenoccursnearcattailmarches.Feedingbeginssoonafterpetaldropandmostofthedamageoccursduringthefollowingthreeweeks.Peakconcentrationsofblackbirdsoccurinmid-September,coincidingwiththecropreachingphysiologicalmaturity.
Control
Acombinationofculturalpracticesmaybeusefultoreducetheriskofblackbirdpredationonsunflowers.Suchpracticesinclude:
• Plantatthesametimeasneighbors–blackbirdsareattractedtoearly maturingsunflowers.
• Donotplantsunflowersnearcattailmarshesorwoodlots-cattailchoked sloughsserveastheroostingsitesforblackbirds.
• Delayedcultivationofcropstubbleincreasesalternatefeedingareasto preventpredationonneighboringsunflowerfields.
• Desiccatetoadvanceharvestandreducetheexposuretimetoblackbirds.
• Decoycroppingtoattractblackbirdsawayfromhighvalueconfectionaryand oilseedvarieties.
• Employscaremethodstofrightenblackbirdsaway.Cannonsareavailable fromyourlocalConservationoffice.
• Cutcattailswhereviableusingamoweroracattailharvester.
Figure 54. Cattails serve as the roosting sites for blackbirds.
50|Blackbirds
55CONTROL TIPS
Noin-cropherbicidesareavailableforcontrolofcockleburinsunflower.Cockleburplantsareshorterandaretypicallynotharvestedwiththesunflowerseed.Useofanall-cropheaderincreasesthepotentialforcockleburseedstobecollectedasitcutsclosertotheground.Croprotationswithsmallgrainsandcultivationhelpmanagecockleburproblems.
Figure 55. Mature cocklebur plant
The Sunflower Production Guide
WEEDSWeedscompetewithsunflowersforresources,limitingcropgrowthandreducingyield.Yieldlossescausedbyweedcompetitionisafactorofweedspecies,density,relativetimeofemergencetothecropandenvironmentalconditions.Weedspeciesdifferincompetitiveability;somecausinghigheryieldlossesonaperplantbasis.
Sunflowersareagoodcompetitoroncethecropisestablished.Weedcompetitionduringtheearlystagesofgrowthhasthelargestimpactonyield,thustheCriticalPeriodofWeedControlinsunflowersisV-EtoV-4.
Thefollowingweedsectionscontainsinformationonspecificweedspeciesthataredifficulttocontrolinsunflower.
Cocklebur
Cockleburhastheabilitytoreducecropyieldsandqualityconsiderably.Itisanannualplantthatusuallygrowsinrangelands,alongroadsides,andinwasteareas.Cockleburissaidtobeoneofthebiggestforeignmaterialproblemsforconfectionarysunflowerprocessors.
Quick ID
Seedling –Longandnarrowcotyledons.Thestembelowthecotyledonsispurplishgreen.Firsttrueleavesaretriangularwithtoothedmargins.Iftheplantispulledup,theremainsoftheburcanbeusedtoconfirmseedlingidentification.
Juvenile–Cockleburhasanerect,ridged,rough-hairystemwithpurplishspots.Leaveshavethreemainveinsandareheart-shapedortriangular.Leavesandstemsareroughtothetouch.
Mature–Femaleandmaleflowersareonthesameplant,butareseparate.Themaleflowersaresphericalandnon-spiny.Thefemaleflowerisgreenandspiny.Ifcrushedtheplantgivesoffadistinctiveodor.
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52|Weeds
CONTROL TIPS
Biennialwormwoodhasnaturaltolerancetomanysoil-appliedandpost-emergencebroadleafherbicides.Wherepossible,pre-emergentfollowedbypost-emergentherbicideapplicationsarethemosteffectivestrategytocontrolbiennialwormwood.Sinceitcangerminateseasonlong,asoilappliedherbicidewithprolongedresidualactivityisneededtoprovideoptimalmanagement.
Sulfentrazonehasshowntohaveupto80%controlofbiennialwormwoodinNDSUtrials,butnodatatosupportthathasyetbeenestablishedinCanada.
Post-emergentherbicidesmustbeappliedtoseedlingslessthan8cmtall.Noin-cropherbicidesareregisteredforcontrolofbiennialwormwoodinsunflower.Forthisreason,croprotationandplanninginpreviouscropsisimportanttomanagetheweed.RefertotheGuidetoCropProtectionforproductsthatcancontrolbiennialwormwood.
Biennial Wormwood
Anative,prolific,small-seededweedforwhichbothannualandbiennialtypescoexist.Traditionally,biennialwormwoodhasbeenclassifiedasanon-croplandweed,andthereforereceivedlittleattentionasamajorarable-landweed.Plantstypicallygrow3to7feettallwithawoodystemaveraging1to2inches(3to 5 cm)indiameter.
Seedlingemergencecanoccurduringtheentiregrowingseasonunderfavorableconditions.Theplantgrowsslowlyafteremergence,remainingasarosetteuntilmidsummer,afterwhichgrowthbecomesrapid.Biennialwormwoodisoftenconfusedforcommonragweed.
Quick ID
Seedling–Cotyledonsareovaloroblongandverysmall(2to3mm).Firsttwoleavesareopposite,ovaltoelongatedhaving2smallteethontheleafmargin.
Juvenile –Formsabasalrosette,short-stalked,pinnatelydividedandre-dividedleavesthatarecoarselytoothed.
Mature –Erect,hairlessplant,withaslenderstemandlittletonobranchinggrowing10to175cmtall.Leavesappeartoformawhorlaroundthestem.Green,inconspicuousclustersofflowersdeveloponshortbranchesintheaxilsofsmallleavestowardsthetopofthestem.Whentheupperleaves,stemandflowerheadsarecrushed,theygiveoffanodorresemblingacombinationofsageandcarrot.
Biennial Wormwood VS. Common Ragweed
Biennialwormwoodhavehairlessleaveswithsharpedges,whereascommonragweedleavesaresmooth,hairyandhaveroundedges.
Figure 56. Biennial wormwood seedling
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Canada Thistle
Isaveryaggressivecreepingperennialthathasthepotentialtocausesignificantyieldloss.Canadathistlespreadsprimarilybyadeep,horizontal,creepingrootsystemformingdensepatches.Itthrivesinawiderangeofsoiltypes,growingbestindisturbedareasandovergrazedpasture.Asingleplantcanproduceover6mofrhizomeperyear.ItistheseundergroundrootsthatmakecontrolofCanadathistledifficult.Canadathistlehasseparatemaleandfemaleplants,whereonlythefemaleplantsproduceseed.Eachplantmayproduceover40,000seeds,whichcanremainviableinthesoilfor21years.
Quick ID
Seedling-Oblongtobroadlyovalcotyledons.Shootsthatemergefromundergroundrootbudslackcotyledons.Firsttrueleavesareovatewithsharpspinesalongmargins(Figure57).
Juvenile-Irregularlylobedleaveswithspinesonlyonthemargins.Plantsvaryintheextentoflobing,lengthofspinesonmarginsandthepresenceorabsenceofhairontheundersidesoftheleaves.Uppersurfaceisshiny.
Mature –Headsformattheendofstemsinclustersmadeofnumerouspinkishpurplediscflowers.Bractsareflattenedandendinshort,weakprickles.
Stemsarehollow,erectandsmooth;spinesmaybepresentnearthebaseoftheplant.
The Sunflower Production Guide
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CONTROL TIPS
MostofthebiomassofCanadathistleplantsisbelowground;thereforekillingtherootsistheonlyeffectivecontrolmethod.Anintegratedmanagementplanisrequiredtoreduceinfestations.Rhizomesareunaffectedbycultivationastheygrowbelowthenormaltillagedepths.Rhizomeshigherinthesoilprofilethatarebrokenbytillagewillproducesmallrootpiecesthatrapidlydevelopintonewplants.Repeatedmowingoftheinfestationthroughoutthegrowingseasonoverseveralyearswilldepletethefoodenergystoredintherootsystem.AvarietyofherbicidesareavailableforcontrollingCanadathistle,butresidualherbicidesaremoreeffective.Fallapplicationsmaximizetranslocationofthechemicalintotherootssincetheplantisputtingreservesintotherootsystemtosurvivethewinter.Springapplicationsjustcausere-sproutingoftheplants.Mosteffectivecontrolisthroughacombinationofspring-summermowing,followedbyafallherbicideapplication.
Figure 57. Canada thistle seedling
Figure 58. Juvenile Canada thistle
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54|Weeds
Kochia
Kochiaisanannualplant,originallyintroducedasanornamentalgardenplant.Sincethen,kochiahasbecomeamajorweedprobleminmanyareasofCanadacausingseverereductionsinyield.
Quick ID
Seedling–Cotyledonsareshortandnarrow,dull-greenontheuppersurfaceandbrightpinkontheunderside.Thefirstleaveshavemanysofthairs.Plantsformabasalrosettewhennotincompetitionwithothervegetation.
Juvenile–Hasanerect,purple-stripedstemthatisheavilybranched.Leavesretainthegreyish-greenappearanceandarehairy.
Mature–Leavesbecomemuchsmallertowardsthebranchtipsresultinginapyramid-shapedplant.Flowersaregreen,lackpetals,andareinconspicuousinleafaxils.Thewholeplantturnsbrightredinthefall.Whentheplantdries,thestembreaksoffatgroundlevelandactsasatumbleweed,scatteringseedsalongitspath.
CONTROL TIPS
Kochiaseedsremainviableinthesoilforapproximatelytwoyears.Forthisreason,preventingseedproductionforafewyearswillnearlyeradicatepopulations.Toadequatelycontrolkochia,anintegratedapproachisrequired.Falloworshorttermperennialforageproductionpreventsseedproduction.Seedlingsarecontrolledbylate-springcultivation.Sulfentrazone(Authority),apre-seedherbicide,isregisteredtocontrolkochia.Mowheavypatchesofkochiainsalineareastopreventseedproduction.Whensprayingseedlings,itisimportanttomaintainwatervolumesintheupperrecommendedrangestoachievesufficientcoverageandpenetratehairsontheleafsurface.Itisimprotanttorotateherbicidegroupsaskochiacanquicklydevelopherbicidetolerance.
Figure 60. Kochia seedlings
Figure 61. Kochia seedlings have densely haired leaves.
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The Sunflower Production Guide
Prairie Sunflower
Wildsunflowergrowstoaboutthesameheightascultivatedsunflower,competingforsunlight,spaceandmoisture.Itisahosttopestsofcultivatedsunflower,reducingyieldandquality.
Quick ID
Seedlings –Oblongcotyledonsandoppositelyarrangedfirstleaves.Oftenfoundonsandiersoils.
Juvenile–Leavesarelanceolatetoovateinshapewithawavymargin,whereasannualsunflowershavedistinctlytoothedmargins.Prairiesunflowerstemsarecoveredwithshorthairs,flattenedtothesurface.Thisiscontrastingtoannualsunflowerswhicharebristlytothetouch.
Mature–Theheadsofprairiesunfloweraresmallerthanannualsunflower.Thecentraldiskflowersarepurplishbrownandflattened.
62CONTROL TIPS
Pre-plantburndownisnecessaryusinganyofthelabeledproducts.SoloorOdysseysprayedinCLEARFIELDhybridsonlyandExpressinExpressSunhybridsonly,hasshowntoprovidecontrolofPrairieSunflower.Applicationoftheseherbicidesinnon-toleranthybridswillcauseextensivedamage.IftherearemanywildsunflowersgrowinginCLEARFIELDorExpressSunsunflowercrops,controlofthewildspeciesisessentialtopreventcross-pollinationwhichcouldcausethewildsunflowertodeveloptolerancetotheseherbicides,diminishingtheeffectivenessofthesetechnologies.ContactyourlocalseeddealertofindoutmoreabouttheCropStewardshipProgram.
Figure 62. Wild sunflower
Figure 63. Wild sunflower leaves have a wavy margin.
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CONTROL TIPS
Betweenrowcultivationorhoodedsprayerherbicideapplicationcanbeusedforcontrolin-crop.Pre-emergentherbicideapplicationsincludingGlyphosateadditionsoffergoodcontrol.Severalpre-seedherbicidesareregisteredandachievefairtogoodcontrolofwildbuckwheat.In-cropherbicidessuchasAssertareratedfairtogood.Bestcontrolisachievedwhenplantsare3inchesorsmaller.ConsultthecurrentGuidetoCropProtectionforupdatedinformationonregisteredherbicidesandapplicationinformation.
Figure 64. Wild buckwheat has arrow shaped leaves.
Figure 65. The cotyledons of wild buckwheat are angled at 120 degrees.
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Wild-Buckwheat
AnannualintroducedfromEuropeincontaminatedseed,thistwiningnaturedplantmakesfieldworkdifficult.Althoughnotascompetitiveinsunflowercomparedtoothercropslikewheat,asignificantseedbankcanbeproducedinsunflowercreatingproblemsinfutureyears.
Quick ID
Seedlings–Linearcotyledonsattachedat120degreestooneanother.Thestembelowthecotyledonsisoftenreddishpurple.Thetrueleavesarearrowshapedwithpointytipsandpointedbasallobes.Apaperysheathisfoundatthebaseofthefirstleaves.
Juvenile–Twininggrowthhabit,slenderstembranchesnearthestem.Tanglingwithcropscancauselodgingandmakeharvestdifficult.
Mature–Greenishpinkflowersareproducedinaxillaryandterminalclusters.
Fieldbindweedandwildbuckwheatareoftenconfused.Thecotyledonsoffieldbindweedareround,leaveshavearoundedtip,lackssheathatthestemnodes,andhasatrumpet–shapedflower.
The Sunflower Production Guide
Redroot Pigweed
Redrootpigweedisacommonweedofcultivatedfields,gardens,andwasteareas.Thisweedhasanextendedgerminationperiod,growsrapidly,andhasahighrateofseedproduction.Redrootpigweedthrivesandcanquicklyout-competesufferingcrops.
Quick ID
Seedlings–Longnarrowcotyledons.Firsttrueleaveshaveanotchedtip,intowhichthemidribextendsasasmallbristle.Thecotyledonsandfirsttrueleavesareredontheunderside.Thetaprootandstemsarealsored.
Juvenile–Erectstems,usuallyhairyandgreennearthetopoftheplantwhilegreenandsmoothnearthebase.Theleavesarediamondshaped,withentiretoslightlywavymargins.Prominentwhiteveinsontheundersideoftheleaf.
Mature–Tinygreenflowersdevelopinbristlyspikesatthetopoftheplant.Theylookandfeelbristly.
CONTROL TIPS
Controlofredrootpigweedisrequiredcontinuallythroughoutthecroprotation.Authorityhasexcellentcontrolandcanbeusedinreducedandnotillagesystems.TheCLEARFIELDandExpressSunsystemsalsoachieveexcellentcontrol.ConsultthecurrenteditionoftheGuidetoCropProtectionforproductinformationandapplicationtips.Inter-rowcultivationorinter-rowhoodedsprayerapplicationscanalsobeemployedforcontrol;chemicalcontrolismostefficaciouswhenmadepriortothe4-leafstage.
Figure 66. Mature redroot pigweed plant
Figure 67. The underside of Redroot pigweed seedling leaves are red.
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CONTROL TIPS
Manyofthepre-seedherbicidesregisteredforsunflowersachievegoodcontroloffalseragweed.Glyphosateburndownatplantingandcultivationarethemostcommoncontrolmethods.Althoughitusuallygerminatesbeforethecrop,acoolspringcandelaygermination.Fewpost-emergentcontroloptionsareavailable.CLEARFIELDsunflowersutilizingOdysseyachievesgoodcontrolandhasresidualactivityforprolongedcontrol,butnotaslongassomeother“imi”herbicides.Cautionisneededwithuseofresidualherbicidesanditisimportanttomanageacroprotationtoavoidplantinganimi-sensitivecropwithintherecommendedtimeperiod.SeetheGuidetoCropProtectionformoredetails.
Figure 68. Mature false ragweed plant.
Figure 69. False ragweed seedling leaves are hairy.
The Sunflower Production Guide
False Ragweed
Alsoknownasmarshelder,falseragweedisarobust,competitiveannualweedofroadsidesandwasteareasthatcangrowupto2mtall.Itproduceslargeamountsofpollencausinghayfever.Whennotinflower,falseragweedresemblessunflowers.
Quick ID
Seedling –Cotyledonsareovalandstalked.Thefirsttrueleavesareopposite,variablylobedwithasoft,hairytexture.
Juvenile–Stemsaresmooth,muchbranchedanderect.Lowerleavesareoftenthree-lobedwhereastheupperleavesarebroad,almostheart-shaped,withcoarseirregular-toothedmargins.Leavesarecoveredwithhairsonbothsurfaces.
Mature–Small,greenishwhiteflowersinbranchingclustersatthetopoftheplant.
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The Sunflower Production Guide
Green and Yellow Foxtail
AnnualsintroducedfromEurope,greenandyellowfoxtailareseriousweedsofcultivatedcrops,gardensandroadsides.Seedsgerminatethroughoutthegrowingseasonwheneverconditionsarefavorable,makingcontroldifficult.
Quick ID
Green Foxtail
Seedling–Thefirstleavesarearchedandhairless.Baseoftheseedlingisoften reddish.
Juvenile-Leafbladesareflatandlightgreen.Themarginsanduppersurfaceofleafbladesmayfeelslightlyroughtothetouch.Theligule(membraneattheinnerbaseoftheleafwheretheleafattachestothemainstem)hasanunevenfringeofhairs.Auriclesareabsent.
Mature–Soft,greenorpurple-tingedbristlyspike-likepanicleresemblesabottlebrush.
Yellow Foxtail
Seedling –Arched,hairlessearlyleaves.Baseoftheseedlingisoftenreddish.
Juvenile –LeafbladesareflatorV-shapedandlooselytwisted.Bladesarehairlessexceptforlong,kinkyhairsontheuppersurfaceoftheleavesnearthebaseoftheblade(completelylackinginGreenfoxtail).Auriclesareabsent.Liguleisafringeofhairsabout3mmlong.
Mature–Spikeletsarelargerthanthoseofgreenfoxtail
CONTROL TIPS
Pre-plantherbicideoptionsareavailablethatcanprovidegoodtoexcellentcontrolofboththeseweedspecies.Post–emergentherbicidesareavailablethatprovideexcellentcontrol.ConsultthecurrentissueoftheGuidetoCropProtectionforcontroloptions.Maintainingwatervolumeisimportanttoachieveadequatecoveragesincetheleavesarenarrow.
Figure 70. Green foxtail seedling have light green leaves and are completely hairless.
Figure 71. Collar region of Yellow foxtail has long hairs on the upper leaf surface.
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60|Appendix
REFERENCESArthur,A.P.,andY.M.Powell.1990.Descriptionofthelast-instarofCochylis arthuriDang(Lepidoptera:cocylidae)andcharactersforseparatingiffromlast-instarlarvaofCochylis hospesWalsingham.Can.Ent.122:627-631.
Berglund,D.R.2007.SunflowerProduction.NDSU.Fargo,N.D.
Bubar,C.J.,S.J.McCollandL.M.Hall.2000.WeedsofthePrairies.AAFRD.
Friskop,A.S.MarkellandT.Gulya.2009.DownyMildewofSunflower.NDSU.http://www.ag.ndsu.edu/pubs/plantsci/rowcrops/pp1402.htm
Royer,F.R.andR.Dickinson.1999.WeedsofCanadaandthenorthernUnitedStates.UOA.
The Sunflower Production Guide
NOTES