Modeling distribution and abundance of soybean aphid in soybean fields using measurements from the surrounding landscape

Soybean aphid (Aphis glycines Matsumura) is a severe pest of soybean in central North America. Outbreaks of the aphid in Ontario are often spotty in distribution, with some geographical areas affected severely, and others with few or no aphid populations occurring in soybean for the duration of the season. Aphids spend summers on domestic soybean and overwinter on buckthorn, a shrub that is widespread in southern Ontario, and is commonly found in agricultural hedgerows and at the margins of woodlots. Aphids likely use both short distance migratory flights from buckthorn and longer distance dispersal flights in the search for acceptable summer hosts. This study aims to model colonization of soybean fields by aphids engaged in early-season migration from overwintering hosts using measurements of soybean field area, perimeter, length of field facing hedgerow or woodlot, length of hedgerow or woodlot face within 4km of a field, and average density of buckthorn in the hedgerow. Akaike’s Information Criterion (AIC) is a statistic which incorporates the likelihood function and the number of parameters which require estimation in a model. AIC was used to rank numerous competing linear, Logit and Probit models using field parameters to predict aphid presence and density. The variable which best modeled aphid density in soybean fields in the early season was the ratio buckthorn density to field area. This study has important implications in predicting areas that are at elevated risk of developing economic populations of soybean aphid and which may act as sources for further infestation.