Revisiting the Economic Injury Level and Economic Threshold Model for Potato Leafhopper (Hemiptera: Cicadellidae) in Alfalfa

Abstract

The economic injury level for potato leafhopper, Empoasca fabae (Harris), in alfalfa (Medicago sativa L.) was developed over 30 yr ago. In response to increasing market value of alfalfa, farmers and consultants are interested in reducing the economic threshold for potato leafhopper in alfalfa. To address this question, caged field trials were established on two consecutive potato leafhopper susceptible crops in 2013. Field cages were infested with a range of potato leafhopper densities to create a linear regression of alfalfa yield response. The slopes, or yield loss per insect, for the linear regressions of both trials were used to calculate an economic injury level for a range of current alfalfa market values and control costs. This yield-loss relationship is the first quantification that could be used to help assess whether the economic threshold should be lowered, given the increased market value of alfalfa.

Keywords: alfalfa; economic injury level; economic threshold; integrated pest management; potato leafhopper.