D3456: A new degree day model to predict western bean cutworm in Ontario, Canada using pheromone traps

Western bean cutworm (WBC), Striacosta albicosta Smith (Lepidoptera: Noctuidae), is a univoltine pest of corn and dry beans native to the Great Plains of the western United States. Insecticides can effectively control WBC; however, proper application timing is crucial for successful management. Two degree day (DD) models are available to predict WBC moth flight and instigate scouting. However, both models have consistently predicted peak flight too late in the pest’s expanded range of Ontario and the surrounding Great Lakes region, complicating effective management and leading to crop injury. Weekly catch and daily temperature data was collected from 978 pheromone traps and 23 weather stations across southwestern Ontario from 2019–2022. Data were used to compare five DD models with three start dates and two upper and lower temperature thresholds. The models included the existing Ahmad (1979) and Hanson (2015) DD models. The Hanson model — with a 1 March start date, 3.3°C and 23.9°C lower and upper developmental thresholds, respectively — was validated as the best-fit in Ontario. Predictions for first and peak moth catch in Ontario were improved by incorporating region, crop, year, and Julian date into the model. The new model allows predictive timings to be calculated for specific crop-regions in Ontario. Further model development would benefit from more comprehensive monitoring of moth numbers using pheromone traps across the province in future years to improve the predictive model.