Estimating the frequency of alleles associated with pyrethroid resistance in Aphis glycines

Soybean aphid, Aphis glycines (Hemiptera: Aphididae), is becoming a challenging pest to manage. Some populations are now resistant to pyrethroids, an affordable class of insecticides used in the North Central region of the US. Molecular markers have been developed to detect alleles associated with pyrethroid resistance, which arises from point mutations within the voltage-gated sodium channel (vgsc) of A. glycines. To investigate the frequency of vgsc-based resistance alleles in field populations, A. glycines was sampled from fields before and after a foliar application of a pyrethroid insecticide. We worked with a group of Iowa farmers who gave us permission to sample aphids from their fields during the summers of 2021, 2022, and 2023. We collected around 2000 aphids from 10 fields across the three years before and after foliar application of a pyrethroid. We hypothesized that the frequency of resistance alleles would increase in A. glycines populations after the application of a pyrethroid. In fields that were treated, the percentage of plants with at least one A. glycines individual and the average count of A. glycines per plant increased. I am currently analyzing the genotypes and haplotypes of A. glycines individuals collected via vgsc amplicon sequencing. Use of these genetic markers could facilitate the detection of resistance in fields and help farmers in making timely management decisions for insect resistance management of A. glycines.