Hormetic and transgenerational effects in spotted-wing Drosophila (Diptera: Drosophilidae) in response to three commonly-used insecticides

Abstract

Although insecticide formulations and spray rates are optimized to achieve lethal exposure, there are many factors in agricultural settings that can reduce the effective exposure of insect pests. These include weather patterns, timing of application, chemical degradation/volatilization, plant structural complexity, and resistant populations. While sub-lethal exposure to insecticides can still have negative impacts on pest populations, they can also lead to stimulatory, or hormetic, responses that can increase the fitness of surviving insects. Sub-lethal concentrations may also produce increased tolerance in the offspring of surviving adults through transgenerational effects. Sub-lethal effects are pertinent for the invasive fruit pest, spotted-wing Drosophila, Drosophila suzukii (Matsumura), because its small size, diurnal movement patterns, and utilization of hosts with complex plant structures, such as caneberries and blueberries, make effective insecticide applications tenuous. In this study, we measured spotted-wing Drosophila survivorship, reproductive performance, and offspring tolerance in flies exposed to sub-lethal concentrations of three commonly-used insecticides (zeta-cypermethrin, spinetoram, and pyrethrin). We found some evidence for hormesis, with survival effects being sex- and concentration-dependent for all insecticides. Males were far more susceptible to insecticides than females, which in some cases exhibited higher eclosion success and reproductive rates when exposed to sub-lethal doses. We did not observe significant transgenerational effects at sub-lethal concentrations, despite trends of increased offspring viability for zeta-cypermethrin and spinetoram. More research, however, is needed to fully understand the role that sub-lethal effects may play in pest population dynamics, insecticide efficacy, and the development of genetic resistance.

Towards a Sustainable Management of the Spotted-Wing Drosophila: Disclosing the Effects of Two Spider Venom Peptides on Drosophila suzukii

“…For instance, Krüger et al [49] conducted a study on D. suzukii, disclosing that a neurotoxic insecticide with action on insect coordination was, however, able to positively affect mating when applied at sublethal doses. Similarly, a study developed by Deans and Hutchison [50] on SWD revealed evidence of the hormesis response to sublethal doses of the insecticides zeta-cypermethrin, spinetoram, and pyrethrin. This study also described survival as being sex-dependent, as males were more susceptible to insecticides than females.…”

Macronutrient regulation in adult spotted‐wing Drosophila and nutritional impacts on susceptibility to three commonly‐used insecticides

“…More research will be needed to determine if additional impacts on adult nutrition exist. In addition, understanding the interplay between nutrition and insecticide resistance will be important, as D. suzukii has demonstrated a propensity to develop resistance to spinosad and zeta‐cypermethrin (Deans & Hutchison, 2022a, 2022b; Ganjisaffar et al, 2022; Gress & Zalom, 2019). Elucidating how nutritional plasticity can affect the evolution of resistance but also whether resistant population have different intake targets will be necessary for better understanding mechanisms of resistance and for making sure relevant diets are used in resistance monitoring bioassays (Deans et al, 2017; Shikano & Cory, 2014a, 2014b).…”

Propensity for resistance development in the invasive berry pest, spotted‐wing drosophila (Drosophila suzukii), under laboratory selection

“…The efficacy of Mustang Maxx® for D. suzukii control is quite high, as it maintains reasonably high residual contact against adults under field conditions. However, issues with ensuring effective contact with adult D. suzukii have been observed in field‐applications, particularly structurally‐complex cultivars such as caneberries 23–25 . Spinetoram (Delegate® WG), produced by Corteva Agriscience (Indianapolis, IN, USA), is a fermentation product of the soil bacterium Saccharopolyspora spinosa and an analog to spinosad (IRAC Group 5) insecticides 26 .…”

“…However, issues with ensuring effective contact with adult D. suzukii have been observed in field‐applications, particularly structurally‐complex cultivars such as caneberries. 23 , 24 , 25 Spinetoram (Delegate® WG), produced by Corteva Agriscience (Indianapolis, IN, USA), is a fermentation product of the soil bacterium Saccharopolyspora spinosa and an analog to spinosad (IRAC Group 5) insecticides. 26 It causes morbidity by disrupting nicotinic/gamma amino butyric acid (GABA)‐gated chloride channels.…”