University of Wisconsin - Madison Madison, Wisconsin
Simplification of agricultural landscapes may disrupt the spatial and temporal continuity of key resources for service providing insects. For example, research has shown that wild and managed pollinators suffer when they experience periods of floral scarcity during the growing season. Less attention has been paid to the consequences of temporal gaps in prey for arthropod natural enemies (NEs). Crop diversity at multiple spatial scales may influence resource patterns for mobile NEs that can track resources over the course of the season. Here I present the results of a pilot experiment testing whether interplanting strips of an early season crop (oats) can enhance natural enemy conservation and biocontrol in a late season crop (soybean) via temporal resource complementation. Plots planted with narrow strips, wide strips, or monocultures of oats and soybean were sampled weekly between June and August for aphids and predators, and a predator exclusion experiment was conducted in August. Results show that aphid abundances were lower and predator counts peaked earlier in treatment plots compared to soybean monoculture, suggesting potential temporal complementation benefits. However, total abundances were highest for both trophic levels in soy monocultures, suggesting the importance of bottom-up drivers (i.e resource concentration) of arthropod population dynamics. Biocontrol services as measured by the predator exclusion experiment did not significantly differ among treatments. Scaling up understanding of temporal resource complementation and NE movement to the landscape level may be a valuable direction for future research.
