Biological responses of Drosophila suzukii (Matsumura, 1931) (Diptera: Drosophilidae) to stresses induced by synthetic and botanical insecticides and temperature

Abstract

The spotted wing drosophila (SWD) Drosophila suzukii (Matsumura, 1931) (Diptera: Drosophilidae), considered a polyphagous pest of Asian origin, has a preference for attacking red fruits. This research was carried out to identify alternative chemical compounds to spinetoram, such as organophosphates, pyrethroids, neonicotinoids, spinosyns, pyrroles and diamides, two essential oils: Eucalyptus globulus; Citrus sinensis (L.) and a major compound (R)-(+)-limonene for the control of D. suzukii adults. In addition, bioassays were carried out to determine the effect of sublethal concentrations of spinosyns, essential oils (EO) of Eucalyptus, orange, and the major compound (R)-(+)-limonene. Finally, we determined the effect of temperature on the biological cycle and the main morphological characteristics of the species (wings, thorax, and ovipositor). The bioassays were carried out using stock from the Molecular Entomology and Ecotoxicology Laboratory (MEET). Adult flies (5-7 days old) were exposed by ingestion and contact with the compounds to determine the dose-response curves of all the compounds under controlled conditions (23-25oC; 60-65% RH, 12h scotophase). Adults were then exposed to determine the sub-lethal effects of spinosyns (LC5, LC10, and LC20), Eucalyptus EO (LC5, LC20), orange EO and its majority compound (LC1, LC5, LC10, and LC20). Subsequently, we evaluated the longevity of the adults, the fecundity of the females, and the body mass of the newly-emerged adults. Finally, two populations of adult D. suzukii flies were acclimatized (20 and 25oC), and monitoring was carried out every 5 generations, from F10 to F30. We determined the life cycle, body mass, and longevity of the adults, and quantified morphometric parameters related to phenotypic plasticity: body size (thorax measurements), width, area length, wing shape, and size, wing spot area in males, width and number of ovipositor teeth in females. Our results indicate that all the compounds tested are toxic and can potentially control D. suzukii adults; however, at low concentrations, spinosyn and EOs produce a stimulating effect on adult survival and reproduction. Finally, we confirmed that temperature has an effect on the phenotypic plasticity of this species, leading to changes in morphology, giving rise to morphotypes that can be easily adapted to environmental conditions, and guaranteeing the reproductive success of this species.