Seasonal development of soybean arthropod communities in east central Illinois

Abstract

Numbers of individuals of arthropod species were sampled by direct observation at four sites in each of three different east central Illinois soybean fields at weekly intervals from plant emergence until harvest. Soybean plant development at each field was monitored throughout the season. The number of species detected in a field was greater at the edge (site A) than in the middle (site D). Site A vs. site D differences in numbers of herbivore species were greater than for predator/parasitoid species. Habitat space development (i.e. plant growth) was correlated with the pattern of soybean field colonization by arthropods: a relatively constant number of species per habitat space existed throughout most of the season in all three fields. The mean number of species per habitat space was higher at site A than at site D for both herbivores and predators/parasitoids. A windbreak at the edge of a field concentrated certain aerially dispersed herbivores at the leeward edge early in the season. Arthropod food webs during most of the season were very complex compared to early season trophic relationships. Suggestions for further study, including investigation of the effects of planting time, row-width, and interplanting on seasonal development of the soybean arthropod community are discussed.