Inseticidas botânicos : vantagens para o percevejo predador Podisus nigrispinus e efeitos letais para Spodoptera frugiperda

Abstract

The predatory insect Podisus nigrispinus is an important biological control agent which mainly acts in the control of defoliating caterpillars such as Spodoptera frugiperda. The use of synthetic insecticides for pest control can negatively impact populations of P. nigrispinus. Therefore, current trends are the adoption of pest management programs which aim to preserve natural enemies. Thus, botanical insecticides can be an alternative to synthetic insecticides. The objective of this study was to evaluate the sublethal effects of the Lippia sidoides essential oil and its major compound thymol on biological and behavioral parameters of the predatory insect P. nigrispinus, as well as the potential of these insecticides to control S. frugiperda. In the first chapter, the effect of sublethal doses of botanical compounds and the synthetic insecticide deltamethrin were evaluated in terms of their development, reproduction and demographic parameters of said predatory insect. Botanical insecticides presented less toxicity to P. nigrispinus than deltamethrin. As a whole, the treatments prolonged the nymph development and reduced the weight of the adult insects. However, no negative effects on reproduction were observed. Besides, botanical compounds increased male longevity and the number of eggs / nymphs per female, indicating possible hormesis effects. There was no difference between treatments for life table parameters, except for R0, which was higher for thymol compared to deltamethrin. In the second chapter we evaluated the toxicity of the compounds S. frugiperda and P. nigrispinus as well as their effects on predator behavior. The essential oil and thymol were toxic to S. frugiperda and selective to the natural enemy. Nevertheless, deltamethrin insecticide caused the opposite effect, being more toxic to the predator, by also reducing its survival more quickly. Deltamethrin and thymol altered the walking behavior of P. nigrispinus. Moreover, predatory insect nymphs spent more time on the untreated side of the arenas indicating repellency / deterrence of this insect to these compounds. Our results highlight the selectivity of the L. sidoides essential oil and thymol over the natural enemy P. nigrispinus, as well as the potential for S. frugiperda pest control.