D3436: Effects of varying cover crops on the density of three major orders of insects in organic soybean fields

One fundamental reason that pests are a problem in agricultural systems may be attributable to monocultures or simplified ecosystems. Plant diversity in agricultural habitats is directly linked to arthropod biodiversity, which can influence pest management through a range of mechanisms including top-down and/or bottom-up effects. We investigated the impact of rye and crimson clover cover crops in an organic soybean field on biodiversity in the soybean canopy. We used flying intercept traps to monitor the density of Coleoptera, Hemiptera, and Hymenoptera weekly for 14 weeks, comparing plots with cover crops (eco-intensified plot) to plots without cover crops (standard plot). Insects were identified to the family level and categorized into pests, natural enemies, and others. Statistical differences were observed between the eco-intensified and standard plots in some families. Among these, all except for Coleoptera: Carabidae and Hymenoptera: Pteromalidae showed higher densities in the standard plot, particularly in the order Hemiptera, where both natural enemies and pests were more abundant. In the eco-intensified plots, natural enemy families such as Carabidae and Pteromalidae, which increased significantly, do not seem to be closely related to potential prey species found within the families Chrysomelidae, Curculionidae, Aphididae, and Pentatomidae, which decreased significantly. Thus, the differences observed in our study appear to be primarily due to bottom-up effects. To gain a better understanding of how plant cover affects insect diversity in these systems, species-level identification of the collected insects and additional experiments will be conducted in future growing seasons.