Browsing by Author "Boersma, Nevill"

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    Impacts of temperature variation on performance, life-history and flight ability of the false codling moth, Thaumatotibia leucotreta (Lepidoptera: Tortricidae)
    (Stellenbosch : Stellenbosch University, 2018-12) Boersma, Nevill; Terblanche, J. S.; Boardman, Leigh; Gilbert, Martin; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.
    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