The Alder Leafminer (Caloptilia alnivorella) is an important pest on alder and a variety of hosts. Alder Leafminer adults typically emerge in spring from overwintered pupae in leaf mines. After emergence they can be targeted by traps or insecticide treatments. The Alder  Leafminer Growing Degree Day Model, developed by researchers, and available on the Pest Prophet app, is a tool growers can use to time  predict adult emergence.

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 the biofix date should be set to March 1st for the Northern Hemisphere.

Growing Degree Day Accumulation and Treatment

After the biofix is set, growing degree day accumulation can begin, using a lower threshold of 50F. Calculating growing degree days can be done using daily high and low temperatures, or using hourly temperature data using the Pest Prophet app.  Adult emergence occurs at approximately 189 GDD(F). These adults can be targeted with traps or insecticides.

Source:

Herms, Daniel. Using Degree-Days and Plant Pathology to Predict Pest Activity. Tactics and Tools for IPM. Chapter 11. 49-59.