Effect of aphids and the surrounding landscape on the abundance of Coccinellidae in cornfields

We determined how the composition and patchiness of eastern South Dakota agricultural landscapes surrounding cornfields and the abundance of aphids in cornfields affected the abundance of adult coccinellids in cornfields. Four species of Coccinellidae were common in cornfields during the three-year study. Five variables describing the composition and patchiness of the landscape surrounding cornfields (% of pasture/grassland, % of wooded land, % of Conservation Reserve Program land, % of wetland, and boundary density) and abundance of aphids in the cornfields were used as predictor variables to construct stepwise multiple regression models to describe the abundance of each species of coccinellid in the cornfields. Regression models explained for 8–45% of the variation in abundance of adult Coccinellids depending on species. Abundance of aphids entered into regression models for three of the four species. The regression coefficient for aphid abundance was positive in models for two species, but was negative in the model for C. maculata. Each of the five landscape variables was included in a regression model for one or more coccinellid species. Results are discussed in relation to the biology and ecology of the species of Coccinellidae that inhabit cornfields in eastern South Dakota.