The Western Bean Cutworm Moth (Striacosta albicosta) is a common and widespread pest on a variety of hosts such as corn and beans. They can be very challenging to control, and different insecticide products may target different life cycle stages (eggs, nymphs, adults) and not affect the pest at the other life cycle stages. For this reason, predicting when different life cycle stages will occur, based on current observations and weather data, can be very helpful. Researchers have developed a growing degree day model for Western Bean Cutworms to help predict when different life cycle stages will occur.

Calculating Growing Degree Day Units

The Western Bean Cutworm growing degree day model uses a lower threshold of 50F for calculating growing degree day units. The growing degree day units can be calculated from daily maximum and minimum temperatures using these thresholds, or by using the Pest Prophet app, which features this model and is easy to set up and use.

Setting the Biofix date

In order to begin growing degree day accumulation, first a “biofix” date must be set which is the first date, after which growing degree day units will begin to accumulate. In the Pest Prophet app, the biofix date can be adjusted for any observed life cycle stages.

For the Western Bean Cutworm model, the biofix date should be set to May 1st for the Northern Hemisphere. The model can then be used to predict the emergence of next generation of adults. Approximately 1320 GDD(F) after the biofix date (when eggs are observed), 25% of adult moths will be observed. Approximately 1422 GDD(F) after the biofix date, 50% Adult moths will have emerged. Approximately 1536 GDD(F) after the biofix date, 75% Adult moths will have emerged.

 

Sources:

University of Nebraska. IPM. Western Bean Cutworm. Growing Degree Day Model.