The Grape Berry Moth (Paralobesia viteana) is a pest on grapes in some regions, such as east of the Rockies in the United States. There can be 3-4 generations per year of Grape Berry Moth. The Grape Berry Moth Growing Degree Day Model, developed by researchers at Michigan State University, and available on the Pest Prophet app, is a tool growers can use to predict 2nd, 3rd and 4th generation egg-laying.

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 Grape Berry Moths, this biofix is set when wild grape blooms near the vineyard. The best date to use is when approximately 50% of the flowers are open on approximately 50% of the wild grape clusters.

Growing Degree Day Accumulation and Treatment

After the biofix is set, growing degree day accumulation can begin, using a lower threshold of 47F. This can be done using daily high and low temperatures, or using hourly temperature data using the Pest Prophet app. Egg-laying of the next generation will occur at approximately 810 GDD (F). Egg-laying of the following generation will occur at approximately 810 GDD (F) after that, or 1620 GDD (F) after the biofix.

These egg-laying prediction times should be used to coincide with insecticide treatments targeting eggs or larvae.

Source:

Isaacs, Rufus. Mason, Keith. Michigan State University Enviroweather Grape Berry Moth Model. 2018.