Effects of local overwintering host density on patterns of field infestation by soybean aphid (Aphis glycines)

The soybean aphid (A. glycines) is a significant pest threat to soybean production. While the soybean aphid is widely distributed across the Midwest, its primary overwintering host, common buckthorn (Rhamnus cathartica), is largely restricted to the northern United States and southern Canada. The relationship between A. glycines and its overwintering host is well understood; however the effect of R. cathartica proximity on the aphid’s ability to invade local soybean fields is unknown. R. cathratica infested woodlots may serve as the primary source of A. glycines for adjacent soybean fields, causing higher aphid populations in areas of high buckthorn abundance. To investigate this possibility, soybean aphids were collected from common buckthorn and soybean plants in landscapes with high, medium and low buckthorn concentrations. A landscape genetic analysis of 96 single nucleotide polymorphisms will be performed to estimate the genetic relationships between soybean aphids from buckthorn and soybean, and determine if populations on buckthorn served as the source for populations on soybean.