Impacts of temperature variation on performance, life-history and flight ability of the false codling moth, Thaumatotibia leucotreta (Lepidoptera: Tortricidae)

Boersma, Nevill (2018-12)

Thesis (MScConsEcol)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: The sterile insect technique (SIT), the process of mass-rearing, sterilizing and releasing sterile insects, can be used to can be used to combat economically important pests by supressing their population numbers as part of an integrated pest management programme. The success of SIT programmes depends upon the production of high-quality, competitive insects for field release. In SIT programmes, the influence of temperature variation during larval development and chilling during storage and their effects on the field performance of adult mass-reared insects are poorly understood but may be a significant avenue for increasing programme efficacy. The use of different temperatures to rear, handle and immobilise insects allows increased quantities of insects to be collected, handled, irradiated, transported and released. Unfortunately, the use of different temperature regimes in the rearing, storage, handling and shipping of insects have poorly understood impacts on the field performance of mass-reared insects. I mainly studied the impact of different developmental temperatures on larvae and treatment temperatures on adults, examining adult performance in the false codling moth Thaumatotibia leucotreta (Meyrick). After larvae were reared at 15, 20 or 25 °C for their full developmental period, the effect of different acute (2 h) temperature treatments (10, 15 or 20 °C) during the adult stage on traits of (i) cold tolerance, (ii) fecundity and (iii) longevity were determined. In addition, I assessed the flight performance of adults in both laboratory and field conditions after they were exposed to chilling (2 °C) for 16 h during the adult stage. The cold tolerance of adults was not influenced by larval acclimation temperature but was affected by sex and adult treatment temperature. Adult fecundity and longevity were affected by larval acclimation temperature, adult treatment temperature and the interaction of these factors with sex. In flight assays, adults exposed to 2 °C for 16 h performed better in colder environments, both in the laboratory and the field, than adults not subjected to pre-release cold treatment. The benefits of chilling for improved field recapture rates, however, depended on the specific ambient temperature upon release. These results suggest a complex, and in some cases sexdependent, interplay of short- and longer-term temperature history across developmental stages for these traits. Further studies of how these and other traits might respond to artificial manipulation, coupled with information on how any induced trait variation impacts field performance, are essential for the SIT and pest management, with far-reaching implications for understanding thermal adaptation of ectotherms

AFRIKAANSE OPSOMMING: Die steriele insek tegniek (SIT), ‘n proses waartydens insekte in massa geteel, gesteriliseer en vrygelaat word, kan aangewend word om pesbevolkings te beheer en peste van ekonomiese belang te beveg as deel van ‘n geïntegreerde pesbeheer program. Die sukses van SIT-programme hang egter af van die produksie van insekte met goeie gehalte wat kan kompeteer met wilde insekte in die veld. Die invloed van temperatuurvariasies tydens larwale ontwikkeling en die effek van verkoeling tydens berging op die prestasie van volwasse insekte in die veld is onduidelik, maar kan gebruik word om die effektiwiteit van SIT-programme te verbeter. Motte word teen verskillende temperature geteel, hanteer en geïmmobiliseer om hul getalle vir versameling, hantering, irradiasie, vervoer en vrystelling te verhoog. Ongelukkig kan hierdie wisselende temperature tydens produksie, hantering en verskeping ook ‘n ongekende effek op die prestasie van volwasse insekte vanuit ‘n insektarium hê. Ek het hoofsaaklik die invloed van temperatuurbehandeling tydens ontwikkeling en volwasse fase op die volwasse kompeteerbaarheid en prestasie van die valskodlingmot Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) ondersoek. Larwes is teen 15, 20 en 25 ˚C vir die volledige ontwikkelingsperiode geteel, en die effek van akute (2 uur) temperatuurbehandelings (teen 10, 15 en 20 °C) tydens die volwasse stadium is daarna op i) kouetoleransie, ii) fekunditeit en iii) lanklewendheid bepaal. Verder het ek ook die effek van kouebehandeling (teen 2 °C vir 16 ure) op die vlugvermoë van volwasse insekte in die laboratorium en in die veld ondersoek. Die kouetoleransie van volwassenes is hoofsaaklik deur geslag en volwasse temperatuur behandeling beïnvloed maar nie deur die ontwikkelingstemperatuur nie. Alhoewel die ontwikkelingstemperatuur en temperatuurbehandeling ‘n beduidende effek op eierlegging en langlewendheid van die volwasse mot het, is die invloed van hierdie faktore afhanklik van die mot se geslag. Verder het lae-temperatuur behandeling (2 °C vir 16 uur) van volwasse motte ‘n betekenisvolle hoër getal hervangste in beide die laboratorium en veld tydens koeler omgewingstoestande opgelewer in vergelyking met motte wat nie aan die kouebehandeling blootgestel was nie. Die verbetering in hervangstes van volwasse motte in die veld wat aan kouebehandeling bloot gestel was is afhanklik van die temperatuur waaraan die volwasse motte blootgestel word tydens loslaat in die veld. Die resultate dui op ‘n komplekse geslagafhanklike wisselwerking tussen kort- en lang-termyn temperatuurgeskiedenis oor al die ontwikkeling stadiums van betrokke eienskappe wat die effektiwiteit van SIT mag beïnvloed. Verdere navorsing met betrekking tot die invloed van kunsmatige manipulasie asook informasie oor die effek van variasie op sekere eienskappe ten einde fiksheid van volwasse motte in die veld te verbeter is noodsaaklik om die effektiwiteit van SIT en plaagbeheer te verbeter met verrykende gevolge ten einde termiese aanpassings van insekte beter te begryp.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105227
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