Climate change and migratory insects; local and continental effects of temperature anomaly on potato leafhopper arrival and severity of infestation

Global warming has affected insect phenologies, but the effects of temperature on phenology of migrant insects have been less well studied outside of Lepidoptera and Aphidoidea. Potato leafhopper, Empoasca fabae (Harris), has been a severe pest in alfalfa and many other crops, and is one of the most significant insect pests in organic potato. PLH overwinters in the Gulf states and in southern pine  forests. We compiled first occurrence dates from earlier publications and direct reports and used infestation severity levels from an earlier published compilation. We analyzed earliest reported arrival dates in 19 states over a 61 year period using models that included average annual temperature anomaly over the 48 contiguous United States and individual annual state anomalies. PLH arrival has advanced from the mid-twentieth century. PLH generally arrive earlier in years with warmer 48-state temperatures, but there is geographic variation in temperature effects. Arrival in states closest to the overwintering range are affected strongly by 48-state average anomaly, while northernmost states are affected by both individual and 48-state anomalies. Warmer years were also associated with higher severity of infestation.