Returns to grasshopper control on rangelands in southern Alberta

Abstract

Economic injury levels (EILs)—the minimum density of insects that would be required to warrant treatment—were estimated for the 4 most common insecticides sprayed on grasshoppers in Alberta. The results indicate that under the assumed conditions spraying was rarely profitable unless the pests were at very high outbreak levels (>30/M2), the benefits of control lasted more than 1 season or the producers' treatment costs were substantially subsidized by a provincial government rebate program. Estimates vary considerably depending on several parameter values. The most important variables were the cost, life, and efficacy of treatments, the derived price of forage, and assumptions regarding grasshopper population dynamics.