Montana codling moth trap-based biofix compared to two fixed biofix models, 2018-2020

Codling moth (Cydia pomonella) is the primary insect pest of apple and pear trees in Montana and can destroy an entire crop if uncontrolled. Understanding the moth's life cycle is important for determining management methods and timing of treatments. The purpose of this study was to compare trap-based biofix (first consistent moth capture in the spring) to two temperature based trap-free models for fixed biofix developed in other apple producing regions. Trap-free models determine a date for fixed biofix using temperature accumulation data (growing degree days) from nearby weather stations. Trap-free models compared in the present study were developed and are used in Washington state and Utah state; compared to Montana, Washington is similar latitude but lower elevation, and Utah is similar to higher elevation, but lower latitude. Results presented here suggest that the Washington state model for fixed biofix more closely aligns with Montana trap-based biofix in the 3 years of the study. Generally, trap-based biofix in Montana occured after the Washington state model fixed biofix growing degree date; we surmise that low evening temperatures and frequent high winds in some parts of the state and certain years could influence trap catch.