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

Abstract

BACKGROUND: Over the past 14 years, the invasive vinegar fly, spotted-wing drosophila (Drosophila suzukii), has become one of the most damaging fruit pests in the United States. With regional economic losses estimated as high as $500 million for moderate infestations, D. suzukii control represents an often-untenable cost to growers. Management relies heavily on chemical control, which may be applied up to nine times in one season. The widespread use of chemical controls has led to concerns about insecticide resistance, and resistant field populations have already been documented in California and Michigan.RESULTS: We cultured sub-populations of three different Minnesota field populations of D. suzukii in the laboratory and exposed them to increasing concentrations of two commonly-used insecticides, zeta-cypermethrin (pyrethroid) and spinetoram (spinosyn). Over the exposure period, the sub-populations experienced an 8-to 45-fold increase in insecticide concentration. We saw significant increases in the median lethal concentration (LC 50 ) values of one sub-population exposed to zeta-cypermethrin and one exposed to spinetoram. Across the spinetoram exposures, we also observed significant reductions in the top mortality values for three different sub-populations. CONCLUSION: Our results suggest that field populations of D. suzukii can develop resistance to zeta-cypermethrin and spinetoram in short periods of time under laboratory selection but that resistance to spinosyns occurs more readily than to pyrethroids. These results support other studies that have documented spinosyn resistance in field populations and in laboratory selections. Resistance evolution to spinosyns is a particularly important issue, as they represent one of few organic insecticide options for D. suzukii.

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

“…The LC 50 value tested for spinetoram was similar to the LC 50 values recorded in field populations by Van Timmeren et al (2018), which were between 13.7 and 25.9 ppm. However, D. suzukii has been documented to develop resistance to spinetoram over short periods of exposure (Deans & Hutchison, 2022a; Van Timmeren et al, 2018). The initial dose–response assays were conducted in August 2020 while the diet‐insecticide experiments were performed in May 2021.…”

“…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).…”

“…We then used this information, along with macronutrient data for different fruit hosts, to design artificial diets that encompass the range of P:C ratios and P + C contents encountered by flies in the field. We measured survivorship, adult lifespan, and female reproductive performance of flies reared on these diets and exposed to a median lethal dose of three commonly used insecticides in the Midwest U.S. region, including the following: zeta-cypermethrin (Mustang Maxx ® ), spinetoram (Delegate ® ), and organic pyrethrin (Pyganic ® ) (e.g., Deans & Hutchison, 2022a). These data will be useful for understanding (1) how host nutritional variability may impact fly nutritional state and (2) how nutritional state may affect fly susceptibility to insecticidal control methods.…”

“…It has also become an established pest throughout Europe, North and South America (Asplen et al, 2015; Hauser, 2011; Lee et al, 2011; Tait et al, 2021), most recently Africa (Boughdad et al, 2021). Moreover, D. suzukii has already developed resistance to several commonly used insecticides, where foliar applications are targeted at the adult stage (Deans & Hutchison, 2022a; Ganjisaffar et al, 2022; Gress & Zalom, 2019; Van Timmeren et al, 2018).…”

Effective delivery and selective insecticidal activity of double‐stranded RNA via complexation with diblock copolymer varies with polymer block composition

“…In recent years, the use of dsRNA as a species-specific bio-insecticide has been the subject of intense investigation due to the need for pest-control agents with new modes of action and improved biosafety profiles to counter the rise in resistance to commonly used chemical pesticides and the widespread ecotoxicity concerns with the field-use of such chemicals. [1][2][3][4][5][6][7][8][9] The specificity of RNAi induced by the application of exogenous dsRNA offers a promising biological alternative to current chemical insecticides to address the aforementioned concerns.…”