The Azalea Whitefly (Pealius azaleae) is an important pest on azaleas in many regions. Overwintered Azalea Whitefly nymphs typically emerge as adults in spring and begin to lay eggs. Depending on weather and location, there are typically two additional generations in a season. Researchers have developed a model, and available on the Pest Prophet app,  to predict adult emergence for each generations, based on 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 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 adult emergence occurs between 448-700 GDD(F) and the next generation of larvae occurs between 1250-1500 GDD(F). The final adult emergence occurs between 2032-2150 GDD(F). These adult generations can be targeted for treatment by insecticides.

Source:

Growing Degree Day Information. Nathan W. Siegert, Deborah G. McCullough and Jeffrey A. Andresen. Michigan State University, 2 October 2015. Web. 25 February 2016.

Using Growing Degree-Days for Insect Pest Management. Thomas Kowalsick and Scott Clark. Cornell Cooperative Extension in Suffolk County, March 2012. Web. 25 February 2016.