Resistance development, stability, cross-resistance potential, biological fitness and biochemical mechanisms of spinetoram resistance in Thrips hawaiiensis (Thysanoptera: Thripidae).

Background: Spinetoram, a new type of spinosyn with novel modes of action, has been used in effective thrips control programs, but resistance remains a threat. In the present study, a laboratory Thrips hawaiiensis population was subjected to spinetoram for resistance selection to investigate resistance development, stability, cross-resistance potential, biological fitness and underlying biochemical mechanisms.
Results: Resistance to spinetoram in T. hawaiiensis rapidly increased 103.56-fold (for 20 generations of selection with spinetoram) compared with a laboratory susceptible population, and the average realized heritability (h ² ) of resistance was calculated as 0.1317. Maintaining the resistant population for five generations without any further selection pressure resulted in a decline in the resistance ratio from 19.42- to 9.50-fold, suggesting that spinetoram resistance in T. hawaiiensis is unstable. Moreover, the spinetoram-resistant population exhibited a lack of cross-resistance to other classes of insecticides, and showed biological fitness costs. The results of synergism experiments using enzyme inhibitors and biochemical analyses revealed that metabolic mechanisms might not be responsible for the development of spinetoram resistance in T. hawaiiensis.
Conclusion: The current study expands understanding of spinosyn resistance in thrips species, providing a basis for proposing better integrated pest management strageties for thrips control programs and defining the most appropriate tools for such resistance management. © 2018 Society of Chemical Industry.
(© 2018 Society of Chemical Industry.)