Insect pest management in cotton文档格式.docx

Insect pest management in cotton文档格式.docx

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Whiteflies

Minorpests

Thrips

Suckingbugs

Beetles

Minorcaterpillarpests

Otherpests

Untiltheintroductionofgeneticallymodified（GM）cotton,themaininsectpestsofcottonwerethelarvaeofHelicoverpaarmigeraandH. 

punctigera.Thesepestsweregenerallycontrolledwithsyntheticinsecticides,whichalsocontrolledthemajorityofothercottonpests.

Now,over90%ofthecottonareaisplantedwithvarietiesthathavebeengeneticallymodifiedtoproducehighlyspecifictoxinsthatkillHelicoverpalarvaeandmostothercaterpillarpestswhentheyfeedonthecottonplant.However,suckinginsectsmayrequiremoremanagementonBtcottoncomparedtoconventionalcotton.

ThegenesusedtoproducethetoxininGMcottonareobtainedfromanaturallyoccurringbacteriumcalled 

Bacillusthuringiensis 

（commonlyknownasBt）.Insect-resistantorgeneticallymodifiedcottonisoftencalled'

Btcotton'

.TheintroductionofBtcottonhasresultedinasignificantreductionofinsecticideusebygrowers.

Aresistancemanagement 

plan（RMP）isessentialtoensurethatthesevaluable 

traitsremaineffective.VisittheCottonCooperativeResearchCentre（CRC）websiteformoreinformation.

Majorpests

Helicoverpa

Helicoverparemainsamajorpestonconventional（non-geneticallymodified）cotton.Thetwospecies-HelicoverpaarmigeraandH. 

punctigera-areverysimilarinbothappearanceandthedamagetheycausetocotton.However,correctidentificationofthespeciesisimportantbecauseH. 

armigerahasdevelopedhighlevelsofresistancetoinsecticides.

Speciescompositioninthecropwillbeinfluencedbythetimeofyearandlocation.Intemperateregions,themajorityoftheH. 

armigerapopulationoverwinterfrommid-MarchonwardsandemergeduringSeptember/October.HelicoverpapunctigeraisusuallythedominantspeciesthroughSeptember,butseasonalvariationcanleadtoearlyinfestationsofH. 

armigerainsomeyears,particularlyinnortherndistricts.

Helicoverpa 

adultsaremobileandproducelargenumbersofeggs, 

leadingtorapidbuild-upofpopulationsunderfavourableconditions.Survivalisinfluencedbythenumberofpredatorspresentaswellasothermortalityfactorssuchaswind,rainfallandtemperatureextremes.

Damage

Incotton,allstagesofplantgrowthmaybeattackedbutreproductivetissueispreferred.Seedlingscanbe'

tippedout'

whenterminalbudsareeaten.Chewingdamagetosquaresandsmallbollsmaycausethemtoshed,andchewingdamagetomaturingbolls 

maypreventnormaldevelopmentandcanleadtosecondaryfungalinfectionssuchasbollrot.

Monitoringandthresholds

Regularmonitoringofthecropforthepresenceoflarvaeand/ordamageisnecessaryinordertomaketimelydecisionsoncontrol.Thisisespeciallyimportantwhentargetingsmallandpossiblyinsecticide-resistantlarvae.

Visualsamplingistherecommendedmethod.Checkatleast30plantsor3separatemetresofrowforevery50 

ha（largersamplesgivemoreaccurateestimates）.Eggsarenot 

necessarilyagoodbasisforthresholdsasnotallhatchandverysmalllarvaehavehighmortalityrates.Assessbeneficialinsectnumbersandnoteparasitisedeggsandlarvae.

Whenmakingpestmanagementdecisionsincotton,insectnumbersalonemaynotbesufficient.Plantmonitoring（fruitload,yieldandmaturity）assistsindecisionmakingwhenpestlevelsarejustbelowthresholdorwhentherearecombinationsofpests.

Thresholdsforconventionalcottondependoncropstageandare:

Seedlingtoflowering:

2 

larvae/mor1 

larvae（>

8 

mm）/m.

Floweringtocut-out:

mm）/mor5 

browneggs/m.

Cut-out:

15%openbolls-3 

15%-40%openbolls:

5 

larvae/mor2 

ThresholdsforBollgardII®

cottonarethesamefortheentireseasonat2 

3 

mm）/min2 

consecutivechecksor1 

Resistance

Helicoverpaarmigeradevelopedresistanceagainstmostinsecticidesinthelate1990s.However,withtheintroductionofgeneticallymodifiedcotton,biopesticidesandmoreselectiveinsecticides,insecticideresistancetoolderchemistryhasdecreasedinrecentyears.Helicoverpapunctigerahasnoknownresistancetoanyinsecticidesbuttheuseofmoreselectiveoptionsisencouragedtohelppreservenaturalenemies. 

Inordertopreventinsecticideresistance,thecottonindustryhasdevelopedtheInsecticideResistanceManagementStrategy（IRMS）.ThisstrategyisreviewedannuallytodelaydevelopmentofresistanceofH.armigeratoconventionalinsecticides.ThecoreIRMSprinciplesinclude:

rotationbetweenchemicalgroupswithdifferentmodesofaction

limitingthetimeperiodduringwhichaninsecticidecanbeused

limitingthenumberofapplicationsofoneparticularinsecticide. 

VisittheCottonCooperativeResearchCentre（CRC）websiteformoreinformation.

Culturalcontrol

Post-harvestcultivation（pupaebusting）toreducetheoverwinteringstageofHelicoverpaisoneofthemostimportantculturalcontrolpracticesavailable.Cultivationtoadepthofatleast10 

cmwilldamageordisturbpupae,sealtheiremergencetunnelsandtrapemergingmoths.Cultivationalsoleavessurvivorsopentoattackbybirds,mice,earwigs,andwaspparasites.

Naturalenemies

Beneficialinsects 

canaffectall 

Helicoverpalifestages:

Predators

Egg:

redandbluebeetle, 

damselbug, 

greenlacewing, 

brownlacewing, 

nightstalkingspiders,and 

variousants

Larvae:

glossy,brownandpredatoryshieldbugs, 

bigeyedbug, 

assassinbug, 

commonbrownearwig,and 

spiders

Pupae:

commonbrownearwig 

andwirewormlarvae

Moth:

spiders

Parasitoids

Trichogrammaspp.andTelenomusspp.

Microplitisdemolitor 

andtachinidflies

bandedcaterpillarparasite

Backtotop

The 

two-spottedmite（Tetranychusurticae）isthemostnumerousmitespeciesoncotton.Otherspecies 

thatmayoccurarebeanspidermite 

andstrawberryspidermite.Mitesliveontheundersideofleavesandaredifficulttargetsforaerialsprays.Mitesprefermorematureleavesandthehighestpopulationsareusuallyfoundnearthetopoftheplantonmainstemnodes3-5belowtheterminal.Heavymiteinfestationsoncottoncanoriginatefromadjoiningfieldsofearlysowncornfromwheretheyarecarriedbyaircurrents.

Miteinfestationsinseedlingcottonrarelyjustifycontrolbutmaybeausefulindicatorofpotentialproblemsandshouldbemonitoredclosely. 

Thefirstsignofdamageisbronzingoftheupperleafsurfacenearthepetioleorleaffold.Asnumbersincrease,the 

leavesturnredandbecomecoveredinfinewebbing,andaffectedleavesmaydryandfalloff.Highmitepopulationscansignificantlyaffectyieldandqualityofcotton.Theearlierintheseasonthatinfestationsdevelop,thegreaterthepotentialofyieldlossandqualitydowngrades.

Startsamplingatseedlingemergenceand 

continueatleastweekly.Atlownumbers,mitesaredifficulttofind.Mitesareoftentoonumeroustocountindividually,soinfestationscanberatedonapresence/absencesystem.InAustralia,theleavesonthethirdtofifthmainstemnode（downfromtheplantterminal）arethebesttosample.

Thegeneralthresholdformitesformostofthegrowingseasonis30%ofplantsinfected.Thethresholddependsmoreonwhenmitepopulationsbegintoincreaseandhowquicklytheyincreaseratherthanthenumberofmites.Toestimatethepercentageofyieldreductioncausedbymites,acharthasbeendevelopedbythecottonindustryforthedifferentcottongrowingregions.

Management

UnderAustralianconditions,mitepopulationsincreaselessrapidlyontheokraleafvarietiesthanbroadleafvarieties.

Miteinfestationsincreaseaftertheapplicationofsomebroad-spectruminsecticidesforcontrolofotherpests.

Controlweedswithinfieldsandalongfieldboundariesthatserveasover-winteringsitesformites.

ForchemicaloptionstocontrolmitesseethelatestCottonCRC'

spestmanagementguide.

Thripsarethemajormitepredatorincotton.Othersincludedamselbug,bigeyedbug, 

ladybirdbeetles, 

brownsmudgebug, 

appledimplingbug, 

brownlacewingadults,and 

tanglewebspiders.

Mirids（Creonitiadesspp）

Animportantsuckinginsectpestofcotton,miridsareabundantincottonfromearlytomidseasonandoccurthroughoutthecottongrowingregionsofQueenslandandNewSouthWales. 

Greenmiridsaremorecommonthanbrownmiridsbutbothcausesimilardamage.

Adultsandnymphsfeedbypiercingplanttissueandreleasingachemicalthatdestroyscellsinthefeedingzone,resultinginthefollowingsymptoms:

localisedleafdamage

terminalwiltingofyoungplants

deformity（broomshaped）

sheddingofsquaresandsmallbolls

damagetobolls（upto15 

daysold）bycausingwartygrowthsinsidecarpelwhichcausesdiscolouredlint

malformedbolls,delayofmaturity

reducedlintandfibrequality.

Miridsareaverymobilepestandpopulationscanfluctuaterapidlysosamplingneeds