Advancing the theory and implementation of economic injury levels for pest management.

The economic injury level is a well-established paradigm in pest management. The concept states that there is a pest density where the cost of damage equals the cost of the insecticide treatment, and this density is used to trigger control actions. The economic injury level thus informs decisions about the need for insecticides based on pest sampling data. However, we argue that the concept often overlooks key biological assumptions about herbivory and typically fails to incorporate the role of crop and pest phenology in optimizing pest sampling and insecticide timing. In this review, we first overview the economic injury level concept and highlight the consequences of these limiting assumptions. We then propose that phenology models that incorporate crop susceptibility and pest life stages, combined with insecticide efficacy data, can allow for better timing of pest management actions. We also suggest that pest monitoring and management decisions should focus on minimizing pest damage accumulation, rather than limiting control actions to predefined thresholds. Future research should focus on effectively leveraging crop and pest phenology models along with field sampling to guide control actions only during the key management times. While the economic injury level has been a historically important concept guiding pest management theory and practice, adapting the concept to specific crop-pest relationships can ensure more efficient use of pest control inputs.