Tephritid fruit flies are highly successful invaders and some—such as the Mediterranean fruit fly, Ceratitis capitata (Wiedemann)—are able to adapt to a large range of crops. Biosecurity controls require that shipments of produce are ensured to be pest-free, which is increasingly difficult due to the ban of key pesticides. Instead, stress-based strategies including controlled atmosphere, temperature, and irradiation can be used to eradicate flies inside products. However, unlike pesticide science, we do not yet have a robust scientific approach to measure cost-effectively whether a sufficiently lethal stress has been delivered and understand what this stress does to the biology of the pest. The latter is crucial as it would enable a combination of stresses targeting multiple molecular pathways and thus allow for lower doses of each to achieve higher lethality and reduce the development of resistance. Using heat as an example, this is the first study investigating the molecular stress response to heat in Tephritidae. Using a novel setup delivering measured doses of heat on C. capitata larvae and a high-density 11 timepoint gene expression experiment, we identified key components of lethal heat-stress response. While unraveling the complete molecular mechanism of fruit fly response to lethal stress would be a long-term project, this work curates and develops 31 potential biomarkers to assess whether sufficient lethal stress has been delivered. Further, as these protocols are straightforward and less expensive than other—omic approaches, our studies and approach will assist other researchers working on stress response.
Larvae of Helicoverpa armigera (Hübner) can develop a form of Bt tolerance after exposure to sub‐lethal doses of Bt‐toxin subclass Cry1Ac. Increasing levels of tolerance are produced over generations of larval exposure, which are not related to DNA sequence changes, and are largely maternally transmitted. The characteristic of maternal transmission, combined with the importance of egg parasitoids to cotton pest management, raises questions about the effects of Bt tolerance/exposure on the eggs of H. armigera and on some key metrics of egg parasitism. In the present study, the effect of inducible tolerance on eggs of H. armigera and parasitism by Trichogramma pretiosum (Riley) is investigated. First, the volumes of eggs laid by susceptible and tolerant H. armigera females are compared. In addition, the effect of inducible tolerance on egg parasitism is determined by comparing parasitism success, the number of adult wasps emerged per host egg, and the proportion of male and female offspring emerged per host egg. The results obtained suggest that Cry1Ac‐tolerance is associated with increased egg volume, even after just one generation of sub‐lethal exposure. When tolerant H. armigera are freed from ongoing sub‐lethal exposure, a corresponding decrease in egg volume is not detected. Although there is no difference in the percentage of eggs parasitized, there is an increase in the number of emergent parasitoids, especially males, from eggs laid by tolerant H. armigera. These results confirm that maternally‐transmitted Bt tolerance is reflected in the phenotype of the eggs of tolerant offspring, which affects egg parasitism.
-Pollen of wind-pollinated plants such as grapevine rapidly dries out and is blown away after the anthers dehisce. Therefore, from the point of view of a pollen-collecting bee, pollen from wind-pollinated flowers is best collected soon after it becomes exposed. In grapevine, pollen becomes available immediately after the calyptra is shed, a process also referred to as capfall. We show, for the first time, that honey bees foraging on grapevine actively remove the calyptra from flowers. Using manual cap removal, we estimate that cap removal increases the pollen yield by 70 % compared to collecting pollen from flowers after capfall. The bees selectively foraged on inflorescences with high numbers of loose caps, thus further enhancing their pollen revenue. We discuss the possible benefits of cap removal by honey bees for the development of individual berries and grape bunches of certain varieties.Apis mellifera / Vitis vinifera / foraging behaviour / calyptra
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