D3449: Baseline susceptibility of the lesser peach tree borer to synthetic insecticides from a population collected in a Michigan tart cherry orchard

The Lesser Peach Tree Borer (LPTB) (Synanthedon pictipes) is a lepidopteran wood boring pest that can cause serious losses in commercial tart cherry orchards in Michigan. Larval feeding under the bark in the scaffolding and trunk causes girdling and facilitates bacterial and fungal infections, leading to the decay of trunk tissue and ultimately resulting in the complete loss of the tree. Traditionally, the primary strategy for managing this pest has involved targeting its larvae with chlorpyrifos. However, due to the negative effects associated with chlorpyrifos, its use has been restricted in Michigan's tart cherry orchards, prompting the need for alternative management tools for the LPTB. Our research explores alternative compounds to chlorpyrifos, with this study aiming to establish a baseline susceptibility of LPTB to insecticides, serving as a reference for comparing LPTB susceptibility in conventional orchards in the future. Using the adult stage of LPTB (moths) as a proxy, we conducted topical bioassays to determine the LD50s of acetamiprid (Nicotinic Acetylcholine receptor competitive modulator 4A) and esfenvalerate (Sodium channel modulator 3A) compared to chlorpyrifos (Acetylcholinesterase inhibitor 1B). Traps baited with lures to attract males were set up in an organic cherry orchard. Each moth was treated with 1 µL of insecticide. Mortality rates were assessed at various intervals post-treatment, and the data were analyzed using Probit Analysis. This constitutes the first report on LPTB susceptibility to insecticides and may be instrumental in estimating the degree of LPTB pesticide resistance/susceptibility in conventional orchards.