Weeds as beneficial sources of plant diversity in high tunnel tomato

Weeds are often viewed as antagonists in agroecosystems because they can compete with crops and provide refuge for invertebrate pests. However, it is possible that weeds serve as beneficial sources of plant diversity that contribute toward pest regulation in agroecosystems. We conducted a two-year study across 15 farms in Indiana, United States to describe the benefits and risks of weeds in tomato high tunnel production systems. At these farms, we identified common weed species and broadly identified invertebrates they hosted. We also measured weed coverage to link “weediness” with pest pressure and insect diversity on a focal crop, tomato. We also conducted a one-year study at our Purdue research farm to refine these observations and extend the impacts of weeds to overall tomato yield. Across farms, weeds did not increase pest risk and was linked to lower pest pressure at our research site. We also found little impact of weed presence on tomato yield or marketability. Natural enemy abundance on tomatoes was largely unaffected by weed presence, although there were some exceptions among particular groups that were all found in higher abundance in weedy tunnels. Chickweed, Virginia pepperweed, foxtail grasses, and cleavers supported relatively high ratios of natural enemies to herbivores, while other weeds hosted both herbivores and natural enemies. Overall, our results suggest that selectively managed weeds can support beneficial invertebrates and contribute to pest suppression without reducing crop productivity.