Effects of artificial defoliation on pennycress (Thlaspi arvense) biomass and yield

Pennycress (Thlaspi arvense) is a winter annual weed species found in temperate regions that is being domesticated as a new winter cover crop and biofuel species in the Midwest of the United States. However, the response of pennycress to different stressors, including insect pests, is still poorly understood. Artificial defoliation has been used successfully to assess potential impacts of insect pests for various crops. In this study, artificial defoliation was used to evaluate pennycress response to stress. Field-planted pennycress was assessed in a randomized complete block design, with six replications of five treatments. The treatments represented 50% and 100% defoliation at two different timings (early timing: vegetative rosette; and late timing: early flowering), and a non-defoliated control. Both timings of 100% and 50% artificial defoliation significantly reduced pennycress biomass and total yield, with both timings 100% defoliation causing the greatest reductions. Seed number and weight was reduced by both 100% defoliation. These results confirm that defoliation can reduce the utility and value of pennycress through reductions in biomass and seed yield. Further investigation is needed with lower levels of defoliation for a better understanding of potential plant response to more typical levels of insect injury. The results of this study bring light to pennycress response to defoliation and can help future development of integrated pest management programs for this new crop.