Spatial Externalities of Pest Control Decisions in the California Citrus Industry

Predaceous and parasitic insects provide control of important citrus pests. However, many pesticides are toxic to these beneficials. Using California citrus grower survey data, this article tests whether landscape-level use of pesticides affects the presence of and reliance on Aphytis melinus, an important beneficial insect. Results show that landscape-level pesticide use decreases the presence of A. melinus and increases reliance on insecticides. Pesticide use on non-citrus crops has a significant negative effect on the presence of Aphytis melinus, suggesting a cross-crop spatial externality. Our findings illustrate that regulations designed to address cross-crop effects on beneficial insects can increase social welfare.