The Douglas-Fir Needle Midge (Contarinia pseudotsugae) is an important pest on pine. Overwintered Douglas-Fir Needle Midge larvae typically emerge in spring and the first adults may be seen soon after. The Douglas-Fir Needle Midge Growing Degree Day Model, developed by researchers at Oregon State University, and available on the Pest Prophet app, is a tool growers can use to predict timing of adult trap catches based on 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 traps can be used.

Growing Degree Day Accumulation and Treatment

After the biofix is set, growing degree day accumulation can begin, using a lower threshold of 39F, and an upper threshold of 110F. This can be done using daily high and low temperatures, or using hourly temperature data using the Pest Prophet app. Adults typically reach peak emergence at 758 GDD (F) after the Jan. 1st biofix. These adults can be targeted for traps or insecticide treatment.

Source:

West, K., Deangelis, J., B. Simko. 1991. The Biology and Control of the Douglas-fir Needle Midge in Christmas Trees. OR St. Ext. Serv. EC 1373