Significance

The emergence rate of new plant diseases is increasing due to novel introductions, climate change, and changes in vector populations, posing risks to agricultural sustainability. Assessing and managing future disease risks depends on understanding the causes of contemporary and historical emergence events. Using a data set of 87,000 museum specimen occurrence records, we find that the occupancy of Bactericera cockerelli - the insect vector of a severe pest of potato crops - has increased over the last century in California. However, these changes appear to be unrelated to climate changes, at least at the scale of our analysis. Our findings demonstrate how this historical macro‐ecological approach provides a general framework for comparative risk assessment of future pest and insect vector outbreaks.