Sod webworm (Pediasia trisecta) is an important pest on turfgrass in some areas. Adults Sod Webworms from overwintered pupae in spring when they can be targeted by traps or insecticide treatments. The Sod Webworm Growing Degree Day Model, developed by researchers, and available on the Pest Prophet app, is a tool growers can use to predict adult emergence in spring, as well as larvae and adult emergence of following generations.

Initiating the Biofix

To properly use the model, the biofix must first be set. This is the date from which growing degree days begin to accumulate. For this model, January 1st is the recommended biofix date, in order to predict adult emergence in spring, as well as larvae and adults of following generations.

Growing Degree Day Accumulation and Treatment

After the biofix is set, growing degree day accumulation can begin, using a lower threshold of 50F. This can be done using daily high and low temperatures, or using hourly temperature data using the Pest Prophet app. First adults will emerge at approximately 380 GDD (F). Egg hatching / larvae emergence, and adult emergence of following generations can all be tracked using the model.

Source:

Tolley, M. P., and W. H. Robinson. 1986. Seasonal abundance and degree-day prediction of sod webworm (Lepidoptera: Pyralidae) adult emergence in Virginia. J. Econ. Entomol. 79: 400-404.