The Rhododendron Gall Midge (Clinodiplosis rhododendri) is an important on Rhododendron and other plants. Rhododendron Gall Midge adults typically emerge in spring from overwintered pupae. These adults lay eggs which result in larvae that can be targeted by insecticide treatments. The Rhododendron Gall Midge Growing Degree Day Model, developed by researchers, and available on the Pest Prophet app, is a tool growers can use to predict larvae 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. Larvae emergence occurs between 192-363 GDD(F). These larvae can be targeted with 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.