Response of Glyptapanteles militaris (Walsh) (Hymenoptera: Braconidae), a Larval Parasitoid of the Armyworm, Mythimna unipuncta (Haworth) (Lepidoptera: Noctuidae), to Different Temperatures

6 Pages·1998·1.9 MB·English

by  L Oliveira

J.HYM.RES.
Vol.7(2),1998,pp.268-273
Response of Glyptapanteles militaris (Walsh) (Hymenoptera:
Braconidae), a Larval Parasitoid ofthe Armyworm,
Mythimna unipuncta (Haworth) (Lepidoptera: Noctuidae), to
DifferentTemperatures
L.Oliveira,R.MeloandJ.Tavares
UniversidadedosAzores,DepartamentodeBiologia,P-9502PontaDelgadaCodex,
Azores,Portugal
—
Abstract. Theeffectoffourdifferenttemperatures(15,2025and30°C),onbiologicalparam-
etersoftheAzoreanpopulationofGh/ptapantelcsmilitaris(Walsh)wasstudied,usingMythimna
unipuncta(Haworth)asthehost.Thirteenbiologicalparametersofthehost-parasitoidinteraction
wereanalysed:percentageofhoststhatdiedwithoutproducingparasitoids;percentageoflarvae
parasitizedfromwhichparasitoidsemerged;percentageofhostssurvivingtopupateafterthe
parasitoid'ssting;egg-larvaldevelopmenttime; pupalperiod; totaldevelopmentaltime;adult
longevity;totalnumberoflarvaeperhost;numberoflarvalparasitoidsthatfailtoemergefrom
eachhost;meannumberofparasitoidsthatemergedfromhostlarvabutfailedtospinacocoon;
meannumberofcocoonsperhost;parasitoidsex-ratio;andfinallyemergencerateofadultpar-
asitoidprogeny.Thepercentageofhoststhatdiedwithoutproducingparasitoidsincreasedwith
increasingtemperature.Developmentaltimessignificantlydecreasedwithincreasingtemperature.
Themeannumberofcocoonsperhost;meannumberofparasitoidsthatemergedfromeachhost
larvabutfailed tospinacocoon; and totalnumberoflarvaeperhostwerehigherwhenthe
temperaturewaslower.Parasitoidsexratioandemergencerateofadultprogenywerenotaffected
bythetemperaturestested.
Mythimna unipuncta (Havk^orth) is the able range, will speed up insect metabo-
mostimportantpestinAzoreanpastures. lismandconsequentlyincreasetherateof
Seriouspopulationexplosionsthatrequire development.Eachspeciesandeachstage
theuseofpesticidesoftenoccur(Tavares inthelifehistorymaydevelopatitsown
1992). Glyptapanteles militaris (Walsh)isa rate(Sedlaceketal1990,Spivacetal.1992,
larval parasitoid ofthe armyworm in all GullanandCranston1994).
islandsoftheArchipelago(Oliveira1996). A previous study of the effect of two
Itisdesirabletoincreasethenaturalpop- different temperatures on the biological
ulation ofG. militaris by field releasesof parametersofG. militaris was performed
waspsproducedinthelaboratory,during by Oliveira (1991, 1992). In the present
thefirstgenerationofM. unipuncta. study, we analyse the effect of two ex-
One ofthe most importantabioticfac- tremetemperatures(15and30°C)andtwo
tors that affect insects is temperature. In intermediate temperatures (20and 25°C),
parasitoids this can influence develop- onsomebiologicalparametersoftheAzo-
ment, fecundity, mortality, sex ratio, col- rean population of G. militaris using M.
oration and other characteristics in vari- unipunctaashost.
ous species (Kaya and Tanada 1969; Yu MATERIALANDMETHODS
and Luck 1988; Klein 1988; Lysyk and
Nealis1988;Spivacetal. 1992). Glyptapanteles militaris used in this ex-
Temperatureincreases,withinafavour- perimentemergedfromnaturallyparasit-
Volume7,Number2,1998 269
htiuzureneddsrMoe.fdSunacioopcuMoniocgntusaellwaerirvsaelea,npdlc.aoGclleredocutiepnds4io0nf0poamnsle- 100 B[I]]dppaeurpaaadstihetodiszthesodshtossts
glass vials until adult females were re-
movedforexperiments.Adultsweresup-
pliedwithhoneysolution(10%).Weused
ashostsM. unipunctalarvaefromlabora-
tory cultures, established from eggs laid
byfield-collectedfemales.
emeOrngetnhcee,thoirndediasoylaatfetderfeamdualltepwaarsapsitwoaisd 2TUempei^ture(°2C.");
ssattlialnrog,wleatrdhveatohoopfsatrMa.wsiatusinzirepeuomnncoetvaei.sdoAlffartteoerdmttthhhieerdpfiairrns--t Flpiaegrr.vaat1e.uroefPseM(rf±c/settnhtiaianngdneaasrdotfieiprnrpuouprna)ct.taeA,d,attedsetfaofduorrandmiudflfpteairrpealnsetitctioezmme--d
asitoid andindividuallykept,untilemer- parisonofproportionswasused.Eachcolumnthat
tgaeinnceero(f4.t5heXpa3rcams)i.toiEdasc,hinhoastpllaasrtviaccwoans- eisntfo(lplo<we0d.0b5)y.aciifferentletterissignificantlydiffer-
supplied with a small piece (Icm^)ofar-
tificialdieteverytwodaysasdescribedby lysed by a test for multiple comparisons
PoitoutandBues(1970)and modifiedby ofproportions (Zar 1996), and theothers
Oliveira (1991). Afterparasitization, each parameters were analysed by non-para-
kgerpotupatofafdiifftfyepraernatstietimzpeedrahtousrtela(r1v5a±e0.w5e°rCe, Cmeotmrpiacri"sKornuskteaslt-sWa(lpli<s"0.a0n5d) M(uSclhteirprleer
20±0.5°C,25±0.5°Cand30±0.5°C),under 1984) to compare the results obtained
75±0.5%R.H.and16:8[L:D]photoperiod. from differenttemperatures. To compare
After larval parasitoid emergence and theeffectoftemperatureonallstudiedpa-
construction of the cocoons, each group rameters,adiscriminantfactorialanalysis
wasmaintainedinaplasticcontainer(4.5 (Thioulouse1989),wasperformed.
sXue3.cmE)mewrigthedahaodlueltcsovweerreedbkyepntylionnttihse- RESULTSANDDISCUSSION
same conditionsand weresupplied with ParasitizedlarvaeofM. unipunctawere
honeysolution(10%)untiltheirdeath. able todevelop normally at the fourdif-
Thirteen biological parameters of the ferent temperatures, with high percent-
host-parasitoidinteractionwereanalysed: agesofhoststhatweresuccessfullypara-
percentage of larvae parasitized from sitized and producing parasite progeny
whichparasitoidsemerged;percentageof (Fig. 1).Howeverthepercentageofpara-
deadhosts;percentageofhostssurviving sitized larvae from which parasitoids
ltoarpvaulpadteevealftoeprmtehnetptairmaes;itpouipda'slspteirnigo;d;egtgo-- eamnder3g0e°dCd(itff=er1e.d98s3i,gnpifi<can0t.0l5y),beatcwheieevnin1g5
tal developmental time; adult longevity; maximumvaluesat15°C.
total number oflarvae per host; number Thepercentageofhoststhatdiedbefore
of larval parasitoids that fail to emerge emergence of the parasitoids increased
fromeachhost; meannumberofparasit- withtemperature.Itwasleastat15°C,in-
oids that emerged from host larva but termedieteandsimilarat20and25°C,and
failed tospin a cocoon; mean numberof mostat30°CfFig. 1). Asignificantdiffer-
cocoonsperhost;parasitoidsex-ratio(per- ence was observed for the percentageof
centageoffemales);andfinallyemergence deadhostsat15and30°C(t= 2.280,p<
rateofadultprogeny. 0.05). The percentage of surviving hosts
The first three parameters were ana- aftertheyhadbeenstungbytheparasit-
270 JournalofHymenopteraResearch
Table1. Mean{±standarddeviation)daysofegg-larvaldevelopmenttimeinMytlniiiiniinnpuucla(Dl),
pupalperiod(D2),andthetotaldevelopmentaltime(Dl +D2)ofGlyp^tapantelcsluilitaris,atfourdifferent
temperatures.
Tempe°rCature XD±2sd
15
Volume7,Number2,1998 271
Table2. Mean(±standarddeviation)numberofGli/ptnfuintclesruilitiiriscocoons,thenumberoflarvaethat
failedtospinacocoon,andthatfailedtoemergefromthehostofMythimnaunipuncia,atfourdifferent
temperatures.
lfmptT.itiirf
272 JournalofHymenopteraResearch
;^30^..
Volume7,Number2,1998 273
baccobudworm(Lepidoptera:Noctuidae).Etwi- dent size and development of California red
ronmcntalEntoitwlcgy,20(1),61-64. scale(Homoptera:Diaspididae)anditseffecton
Thioulouse,J.1989.Statisticalanalysisandgraphical hostavailability fortheectoparasitoid,Aphitis
displayofmultivariatedataontheMacintosh. melinus DeBach (Hymenoptera: Aphelinidae).
CominiterApptlicntionsin theBiosciences, 5,287- EnvironmentalEntomologii,17(2),154-161.
292. Zar,J.H.1996.Biostattsticalanalysis.Prentice-HallIn-
Yu,D.S.andR.F.Luck1988.Temperature-depen- ternationalEditions,London,1-662.