Wooded field margins increase potential for cultural and biological control of soybean pests

Crop field margins provide benefits to growers by inhibiting pest dispersal through cultural control and provisioning resources for predators through conservation biological control. The purpose of this study was to elucidate potential soybean insect pest control measures by determining the relationships between pests and spiders, common generalist predators in agroecosystems, and field margin type and distance from the field (0-3 and 3-6 m). Both margin type and distance were significantly correlated with in-field pest abundance (both pooled and taxa-specific). Generally, pest abundance was negatively correlated with the presence of wooded field margins at both distances and could be due to cultural control as hedgerows provide similar ecosystem services in other cropping systems. Spider abundance and spider-pest spatial associations (an indication of potential predation events) within fields were positively correlated with wooded margins from 3 to 6 m, indicating that conservation biological control in addition to cultural control might be contributing to diminished pest abundance in fields with these margins. The lack of wooded margin influence from 0 to 3 m might indicate a need for a minimum wooded area before margins can become a source for within-field spider populations. Furthermore, the number of spider-pest spatial associations was greatest early in the season when pest abundance was lowest and pests were more likely to be spatially aggregated. These data indicate that growers might be able to maintain their field margins, particularly wooded areas, to maximize both potential cultural control and conservation biological control resources, particularly early in the growing season.