One of the approaches to increasing sustainability and long-term resilience to climate change in agricultural systems is incorporating cover cropping into business-as-usual crop rotations. Although agronomists and producers are experimenting with cover crops, the implications for insect pest management, biological control, and pollination are largely unknown. In 2019 and 2020, we conducted an on-farm study by sampling 52 fields (26 cover crops and 26 wheat) in low and high precipitation zones in the inland Pacific Northwest to compare bee communities between wheat and different cover crop mixtures. Using blue van traps and yellow bowls filled with diluted soapy water, we trapped bee pollinators from each field during the peak flowering of cover crops. Cover crops increased abundance and richness but not diversity and evenness of bees. Bee community composition was not different between wheat and cover crops (p = 0.29), but indicator species analysis indicated that Andrena prunorum, Lasioglossum s. str., Melissodes sp.1, and Halictus confusus (all p = < 0.05) were associated with cover crops. The number of species in cover crop mix and weed richness each had weak positive associations with bee abundance (p = 0.06). Cover crop biomass was negatively associated (p = 0.01) with weed abundance, but not with bee abundance and richness. While alternative cereal-based production systems could increase certain metrics of pollinator communities, current cover crop adoption in the region is not sufficient to support more diverse pollinators than business-as-usual.
