Host plant tolerance and planting date influence alfalfa mosaic virus incidence, symptom severity, and yield in chile peppers

Abstract Alfalfa mosaic virus (AMV) is transmitted nonpersistently by multiple aphid species and has become an emerging threat to chile pepper production in regions of the United States where peppers are grown in the vicinity of alfalfa, the primary reservoir of the pathogen. Because nonpersistent transmission limits the effectiveness of chemical vector control, management strategies that reduce exposure to viruliferous aphids are needed. We evaluated how planting date and varietal susceptibility shape AMV incidence, symptom severity, and yield in two chile pepper ( Capsicum annum L.) varieties in a region where peppers are grown near alfalfa, a primary reservoir of AMV and source of dispersing aphids. Across two years, early plantings had the highest AMV incidence and symptom severity, which coincided with pronounced early season peaks in aphid abundance. The putatively tolerant variety consistently showed lower AMV incidence and reduced severity than the susceptible variety, regardless of planting date. Despite greater virus pressure, early plantings produced the highest yields, reflecting the longer production window and the capacity for yield compensation, particularly in the tolerant variety. Late plantings reduced AMV incidence but produced the lowest yields because of shortened growing seasons. These results indicate that planting date strongly mediates disease risk and productivity and that varietal tolerance provides additional protection without altering the effect of planting date. Together, optimized planting timing and selection of tolerant varieties offer practical, complementary strategies for managing AMV in regions where dispersing aphids drive infection risk.