Developing IPM tactics for a new virus transmitted by aphids to chile peppers

Alfalfa mosaic virus (AMV) is a virus transmitted to plants by aphids in a non-persistent manner. The virus was first identified in chile peppers in Southern Colorado in 2019. The goal of this research was to explore management strategies to suppress the virus given its devastating impact on the yield and quality of chile peppers. The objectives were to: 1) determine whether chile peppers have innate tolerance/resistance to AMV using 30 different varieties and mechanical inoculation in a greenhouse, 2) determine the timing and severity of AMV and aphid densities in chile peppers in the field, and 3) test the effectiveness of planting date modifications (early, conventional, late) and tolerant/resistant varieties to suppress the virus in the field. We found significant differences among varieties of chile peppers in the severity of AMV symptoms. In the field experiment, we found that the variety Joe Parker tended to have high AMV symptoms in the greenhouse and was also highly susceptible to AMV in the field. On the other hand, the variety Mira Sol that appeared to have tolerance to the virus in the greenhouse screening assay had low incidence of AMV symptoms and low AMV titers in the field as well. Planting date also played an important role in symptom severity, where late planted peppers had significantly lower severity of AMV symptoms than peppers planted at conventional and late planting dates. These differences were reflected in the yield and quality of peppers harvested in the field.