The Bronze Birch Borer Agrilus anxius) is an important pest on a variety of trees. Overwintered Bronze Birch Borer larvae typically emerge in spring and the first adults may be seen soon after. There can be 2 generations in a year, depending on the weather. Insecticide treatments targeting 1st or 2nd generation larvae are typically the best way to control Bronze Birch Borer populations for the entire growing season. The Bronze Birch Borer Growing Degree Day Model, developed by researchers at Michigan State University, and available on the Pest Prophet app, is a tool growers can use to predict egg hatch based on adult trap catches and field-specific temperature data.

Initiating the Biofix

To properly use the model, the biofix must first be set. This is the date that will serve as the starting point for growing degree day accumulation. For this type of model January 1st is the standard biofix to start accumulation (for the Northern Hemisphere). This can be used to predict when adults will emerge and pheromone traps can be used.

After adults are observed and confirmed, the biofix can be adjusted in order to improve accuracy of the model for predicting later life stages.

Growing Degree Day Accumulation and Treatment

After the biofix is set, growing degree day accumulation can begin, using a lower threshold of 50F. This can be done using daily high and low temperatures, or using hourly temperature data using the Pest Prophet app. Adults typically emerge at 400 GDD (F) after the Jan. 1st biofix. These adults can be targeted for traps. Larvae emerge at approximately 200 GDD(F) following adult emergence. Larvae at this stage can be targeted for insecticide treatment.

Source:

Herms, D.A. Using degree days and plant phenology to predict pest activity. Chapter 11. Tactics and Tools for IPM.