The Azalea Bark Scale (Eriococcus azaleae) is an important pest on azalea and other plants. Azalea Bark Scale crawlers typically emerge in spring from overwintered nymphs. After emergence they can be targeted by traps or insecticide treatments. The Azalea Bark Scale Growing Degree Day Model, developed by researchers, and available on the Pest Prophet app, is a tool growers can use to time  predict crawler 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.  First generation crawler emergence occurs at approximately 957 GDD(F). These crawlers 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.