Assessing practical resistance and fitness costs of pyrethroid resistant soybean aphid

Abstract

The soybean aphid remains the most economically important arthropod pest of soybean in the Upper Midwest Region even twenty years after its arrival in the United States. After years of sustained insecticidal pressures placed on the aphid, anecdotal reports of insecticides failing to control soybean aphid began to emerge, and resistance to the pyrethroid class of insecticides has since been documented in the laboratory. The reduction in the efficacy of field applications of pyrethroids against soybean aphid has not been thoroughly examined, nor the effects of this resistance on aphid fitness. A time-series was created of data from insecticide efficacy trials performed at two locations in Minnesota spanning 2005 – 2020 and changepoint-regression models were used to evaluate percent control over time. Also, the fitness of aphid populations displaying resistant and susceptible phenotypes to pyrethroid insecticides were compared across several experiments over three soybean growing seasons.