ECOLOGICAL AND PHYSIOLOGICAL ASPECTS OF AESTIVATION-DIAPAUSE IN THE LARVAE OF TWO PYRALID STALK BORERS OF MAIZE IN KENYA in mi •»> ••• - OOOO 0086 promotor:dr .J.d e Wilde,hoogleraa r inhe t dierkundig deelva nd e planteziektenkunde. Inn $z.o /i 3.si P. SCHELTES Ecological and physiological aspects of aestivation-diapause in the larvae of two Pyralid stalk borers of maize in Kenya Proefschrift terverkrijgin g van de graad van doctor ind e landbouwwetenschappen, op gezag vand e rector magnificus, dr.H.C.va n der Plas, hoogleraar in de organische scheikunde, inhe t openbaar te verdedigen opwoensda g 6 September 1978 des namiddags tevie r uur ind e aula van deLandbouwhogeschoo l teWageningen . BIBLIOTHCE* vv'-' ••-••>\GEIV ah iwi$6-os MhJZlot 7%/ STEU.TNCEN I Doord egrot everscheidenhei d ind eaar dva nd eperiodiek erusttoestan dva n insektene nd emechanisme ndi ehieraa ntengrondsla g liggeni selk eklassifikati e vand erusttoestand ,gebaseer d opextern eekologisch efaktore n (tliiller)o fo p internefysiologisch everanderinge nbinne nhe tinsek t (Mansingh)gebrekki ge n daardoorbetrekkelij kzinloos . MilllerH.J . (1970)Nov aAct aLeopoldin a35 ,1-27 . MansinghA . (1971)Can .Ent .103 ,983-1009 . Ditproefschrift . II Hetverdwijne nva nd ekutikulair epigmentati eal skriteriu mvoo rd ediapauz e dientme tvoorzichtighei d teworde ngehanteerd . Ditproefschrift . Ill Konklusiesal sdi eva nHiran obetreffend ed elarval egroe iva n Chilo suppressalis end e<irooagewich tbestanddele nva nhe tdoo rdez erijststengelboorde rgenuttigd e voedsel zijnaanvechtbaar . HiranoC . (1964)Bull .Nat .Inst .Agr .Sci. ,Ser .C , no.17 . Ditproefschrift . IV Dekonklusi eva nChippendal ee nRedd yda td eindukti eva ndiapauz e ind e "southwestern cornborer " Diatraea grandiosella een"extremel ytemperature - dependentprocess "is ,waarbi jfotoperiod eee nondergeschikt ero lspeelt ,berus t oponvoldoend egegevens . ChippendaleG.M .an dRedd yA.S .(1973 )J .Insec tPhysiol . 19,1397-1408 . V Debewerin gva nUsu ada te ree nkausaa lverban dbestaa t tussenhe toptrede n vandiapauz e ind emai sstengelboorde r Busseola fusoa engelijktijdi gvoor - komendeveranderinge n ind esamenstellin gva ndien swaardplan t iszuive r spekulatief. UsuaE.J . (1973)Ent .exp .& appl . 16,322-328 . VI Het toekennenva nee nkeuringscertifikaa taa nbepaald efruitgewasse ndoo rd e + . NAK-B isgee nenkel egaranti evoo rd elevensvatbaarhei dva ndi egewasse nindie n zei nhe tnajaa ri npakkette nworde naangebode ne ni sdu smisleiden dvoo rd e konsumentent. + NAK-B NederlandseAlgemen eKeuringsdiens tvoo rBoomkwekerijgewassen . VII Dediskrepanti e tussend eautomatisch evermeldin gva nd ema ni nhe tpaspoor t vanzij nechtgenot ee nd eonmogelijkhei d voord ema nzij nechtgenot e inzij n paspoort tevermelde ni see nsymptoo mva nd eopgedronge nonafhankelijk ero l vand ema ni nd ehuidig emaatschappij . Paspoort instruktieNederlan d 1952,art .23 . VIII Doord esterk einvloe dva n"tribalism "o pd emaatschappelijk estruktuu rva n velederd ewerel d landen,worde nta lva nontwikkelingsprocesse nernsti g bemoeilijkt. IX Debezware nva nKenyas eautoriteite n tegenhe tdrage nva nd etraditionel ekledi j doord eMasa izij nonjuis te nleide nslecht s totonnodig eirritatie . X VeleNederlander s tonenplotselin g eenbete rbegri pvoo rhe t levensritmeva n volkereni ntropisch egebiede n tijdensee nhittegol f dantijden snormaa li n Nederlandvoorkomend etemperaturen . Proefschriftva nP .Schelte s Ecological andphysiologica l aspectso faestivation-diapaus e inth elarva eo f twoPyrali dstal kborer s inKenya . Wageningen,6 Septembe r1978 . Contents 1 GENERAL INTRODUCTION 1 2 THE INCIDENCEO FAESTIVATION-DIAPAUS EA SRELATE DT O CLIMATE 3 2.1 Introduction 3 2.2 Literature 3 2.3 Materials andmethod s 8 2.3.1 Rearingmethod s 8 2.3.1 Criterion fordiapaus e 9 2.3.3 Fieldexperiment s 10 2.3.4 Effects ofphotoperio d andtemperatur e 11 2.4 Results 12 2.4.1 Drought resistance as criterion fordiapaus e 12 2.4.2 Field experiments 14 2.4.2.1 Climate during fieldexperiment s 14 2.4.2.2 Seasonal fluctuations in larval andpupa l populations 15 2.4.2.3 Seasonal incidence ofdiapaus e 15 2.4.3 Effects ofphotoperio d and temperature 20 2.5 Discussion 22 3 THETIMIN GO FTH EPERIO DO F DIAPAUSE INDUCTION;SOM EBEHAVIOURAL , PHYSIOLOGICALAN DMORPHOLOGICA L ASPECTSO FAESTIVATION-DIAPAUS E 26 3.1 Introduction 26 3.2 Literature 27 3.3 Materials andmethod s 30 3.3.1 General 30 3.3.2 Behavioural studies 30 3.3.3 Physiological studies 31 3.4 Results 32 3.4.1 Construction ofrestin g sitean d spinningbehaviou l 32 3.4.2 Feedingbehaviou r 33 3.4.3 Physiologyo fnon-diapaus elarva e 35 3.4.4 Physiologyo flarva eenterin gdiapaus e 38 3.4.5 Morphologicalchange si nlarva eenterin gdiapaus e 43 3.5 Discussion 46 THEINCIDENC EO FAESTIVATION-DIAPAUS EA SRELATE DT OTH ECONDITIO N OFTH EHOS TPLAN T (MAIZE) 51 4.1 Introduction 51 4.2 Literature 51 4.3 Materialsan dmethod s 53 4.3.1 Handlingo fsample s 53 4.3.2 Analysiso fste mmateria l 54 4.3.3 Consumptionan dutilizatio no fmaiz estem s 55 4.4 Results 55 4.4.1 Diapausean dstag eo fmaiz e 55 4.4.2 Diapausean dchemica lcompositio nmaiz estem s 57 4.4.3 Compositiono fth emaiz este mdurin git snorma l development 59 4.4.4 Consumptionan dutilizatio no fmaiz e 60 4.5 Discussion 61 EFFECTSO FNATURA LAN DARTIFICIA LFOO DO NTH EINDUCTIO NO F AESTIVATION-DIAPAUSE 67 5.1 Introduction 67 5.2 Literature 67 5.3 Materialsan dmethod s 69 5.3.1 Larvalmateria l 69 5.3.2 Experimentswit hmaiz e 69 5.3.3 Experimentswit hartifica ldiet s 70 5.3.4 Studieso nth ephysiologica lconditio no flarva e 72 5.4 Results 72 5.4.1 Responseso flarva et oage dmaiz eplant s 72 5.4.2 Sensitivityo flarva et oage dmaiz eplant s 75 5.4.3 Larvalgrowt han dpupatio no ndiet s 77 5.4.4 Pigmentationan dphysiolog yo flarva eo ndiet s 78 5.4.5 Sensitivityo flarva et odie t 80 5.5 Discussion 83 HORMONAL INVOLVEMENT INAESTIVATION-DIAPAUS E 86 6.1 Introduction 86 6.2 Literature 86 6.3 Materials andmethod s 87 6.3.1 Juvenile hormone titre 87 6.3.2 Head ligatures and injections with 0-ecdysone 88 6.3.3 Experiments with JH-analogues 88 6.4 Results 89 6.4.1 Juvenile hormone titre during diapause induction, maintenance and termination 89 6.4.2 Effects ofhea d ligatures and/or B-ecdysone on diapausing larvae 90 6.4.3 Effects of JHA onnon-diapaus e larvae 91 6.5 Discussion 94 SUMMARY 97 SAMENVATTING 100 ACKNOWLEDGEMENTS 103 REFERENCES 104 CURRICULUM VITAE 110 1 General introduction Stemborer sar ebein gconsidere da smajo rpest so fman yGraminea eal love r theworl d (JEPSON1954 ,METCAL Fan dFLIN T1967 ,HIL L 1975).Al limportan t graminaceouscrop ssuc ha smaize ,millet ,rice ,sorghu man dsugarcan e- ofte n thesubsistenc efoo dcro pi ndevelopin gcountrie s- ma yseriousl yb eaffected . Inth etemperat eregion srelativel yfe wimportan tste mborer sar eknown .Ver y notoriousar eth esouthwester ncor nbore r Diatraea gvandiosella andth eEuropea n cornbore r Ostvinia nubilalis, bothPyralidae .I nth esubtropic san dth etropic s stemborer sar emuc hmor eabundant .Well-know ndestructiv eexample sar efoun d amongth eNoctuida ee.g .th emaiz ebore r Busseola fusoa (maize,sorghum) ,th e pinkstal kbore r Sesamia oalamistis (maize,sorghum ,millet ,rice ,sugarcane) , andth epurpl este mbore r S. inferens (rice,sugarcane )an damon gth ePyralida e e.g.th espotte dstal kbore r Ch.Ho partellus (maize,sorghum ,millet ,sugarcane , rice),th ecoasta lstal kbore r C. oriahalooailiella (maize,sorghum ,millet , sugarcane),th eric este mbore r Chilo suppressalis (rice,maize) ,th esugarcan e stalkbore r Eldana saacharina (sugarcane,maize ,sorghum )an dsevera l Tryporyza spp. (rice)(HIL L1975) . Thelife-cycl ean ddamag eo fal lborer si sver ysimilar .Normall yegg sar e laido nth eundersurfac eo fyoun gleave so rbetwee nlea fsheath san dstems .Afte r hatchingth eyoun glarva efee dactivel yo nth etende rleave sbu ta ssoo na sthei r sizeincrease sthe ybor eint oth estems .I nyoun gplant slarva eattac kth e growingpoin tan dcaus es ocalle d 'deadhearts' .I nolde rplant sth ecaterpillar s boreint oth emai nstem ,whic hsubsequentl yi shollowe dou tove ra considerabl e length.Plant sthu saffecte dhav ea poo rgrowth ,a reduce dyiel dan dar emor e susceptiblet owin ddamag ean dsecundar yinfections .Smal lan dwea kplant s usuallysuffe rmor efro mbore rattac ktha nhealth yplants .I ntropica lEas tAfric a wherecrop sar eregularl ygrow nunde radvers econdition s (unpredictablerainfall , poorsoils )thi sha softe nbee ndemonstrate d (COAKER1956 ,MATHE Z 1972,HIL L 1975). Insuc hcase sste mbore rdamag ema yb edisastrous .Whe nlarva ear efull ygrown , theystar tpreparin gfo rpupatio nb ycuttin ga nexi thol ei nth este mt oenabl e theemergin gmoth s toescape .Th e life cyclema yb e continuous inarea swher e suitable conditions forgrowt h ofth ehos tplan t arepermanentl ypresent .Usuall y however thecycl e isinterrupte db y acol do rdr y seasondurin gwhic hplan t growth isimpossible .Th e larvae thenente r diapause (called Ihibernation'whe n occurring during acol d season and 'aestivation'whe n inth edr y season) inside the old stems orstubble .O nretur no f favourable conditions,pupa edevelo p andth e emerging moths oviposit onth enewl yplante dhos tplants . Chemical control ofste mborer sha s oftenprove d tob e ratherunsuccesful . Best results are obtained inth eearl y season against theyoun g larvaewhic hhav e justhatche d from theegg s laidb ymoth swhic hha ddevelope d from diapausing larvae.Olde r larvaehav epenetrate d the stalks inwhic h they arewel l protected against insecticides.Th e durationo flarva l development,varie swidel ywithi n one population ofste mborer s and after themor e or lesssynchronou s development of the 1stgeneratio n attacking the crops,al l developmental stages ofborer s can soonb e foundwithi n one field.