Entomological considerations for domestication of pennycress, Thlaspi arvense, as a cash cover crop

Abstract

Pennycress (Thlaspi arvense L.), a common annual weed in temperate regions, is being domesticated as a winter cover crop and oilseed crop for the Midwest U.S. corn-soybean rotation. This domestication presents significant agricultural and environmental benefits; however, understanding of the interactions between pennycress and insect herbivore communities and agroecosystems remains limited. This research aimed to fill these knowledge gaps and support the development of integrated pest management (IPM) programs for this emerging crop.First, a comprehensive review was conducted to compile available information on the insect herbivores, natural enemies, and pollinators associated with pennycress, as well as its response to stressors such as defoliation, stem injury, and stand loss. The review highlighted the need for further research to develop effective IPM strategies. Second, field experiments were conducted over two years to assess the impact of artificial defoliation on pennycress biomass, yield components, and oil and protein content. The experiments, which tested various defoliation levels and timings, revealed that significant reductions in biomass, yield and protein content occurred, particularly during critical growth stages such as the rosette and flowering periods. These findings emphasize the importance of timing in managing defoliation to minimize crop loss. Finally, field experiments were performed to evaluate the impact of relay-cropping soybean with pennycress on soybean aphid populations. Across four site-years in Minnesota with relatively low levels of soybean aphid infestation, relay-cropping soybean with pennycress generally reduced soybean aphid densities compared to soybean without pennycress. This suggests that pennycress could serve as a sustainable pest management tool in soybean production, while also enhancing other aspects of economic and environmental sustainability of the corn-soybean rotation system.