Assessing pest control treatments from phenology models and field data

Abstract

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.