Implications of Simultaneity in Pest Damage Functions

Kelly M. Cobourn, Boise State University
Hannah J. Burrack, North Carolina State University
Rachael E. Goodhue, University of California, Davis
Jeffrey C. Williams, University of California, Davis
Frank G. Zalom, University of California, Davis

Abstract

The prevalent approach to formulating a damage function, which links biological and economic systems, defines yield loss at harvest as a function of a pest’s local population. This type of damage function, however well it fits the data, misrepresents causality. We specify a structural damage relationship that explains infestation by the olive fruit fly in California. Estimation using an exceptional dataset indicates that weather and management practices simultaneously affect fly populations and fruit susceptibility to damage. Comparison of the structural model with a population-based approach suggests that intra-seasonal damage rates are more responsive to changes in host susceptibility than to variations in fly populations.