Assessing pest control treatments from phenology models and field data

Efficacy of insecticides is often determined from apparent yield loses due to a target pest. However, pests can affect yields even when controls work as expected. Further, most pest populations are monitored through adult counts without procedures to assess dynamics of immature stages. Here, we propose a framework to assess the efficacy of control treatments from adult counts in non-experimental setups based on the shifts in temporal patterns of adult emergence caused during the residual period of treatments applied to kill immatures. We use phenology models scaled to field counts to track the stage structure of pest populations across a season and produce reference population trajectories with and without the treatment. Field-collected trajectories are then classified as with or without an effective control through a time-sequential probability ratio test. The method was evaluated using pheromone trap captures of codling moth, Cydia pomonella, and four of the most widely implemented treatment programs in apple and pear orchards.

Simulations revealed that when field-collected trajectories are classified as treated with a control, there is 70% chance that the treatment program is > 50% effective, or that the program is < 66% effective when field-collected trajectories are classified as untreated, provided the trajectories are made of ≥ 15 pheromone traps.

This framework is a powerful, evidence-based tool to optimize the selection of inputs and application protocols for pest control and could be applied to virtually any pest that can be sampled regularly and whose phenology can be modeled as a function of degree-days. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.