Western Cherry Fruit Flies are an important economic pest on cherries in a variety of areas, especially the Pacific Northwest. Researchers at Oregon State University have developed a growing degree day model for Western Cherry Fruit Fly that can help predict when adult emergence from overwintered pupae, as well as egg-laying, egg hatch and pupation of the following generation.

Calculating Growing Degree Days

The Western Cherry Fruit Fly model uses a lower threshold of 41F. It can be calculated with daily high and low temperatures, using the sine model to estimate growing degree day units, or the Pest Prophet app can be used to calculate GDD accumulation from hourly temperature data for a specific field.

For this model, the “biofix” date, or date from which to start accumulating growing degree days, should be set to March 1st for the Northern Hemisphere.

First adult emergence occurs at approximately 832 GDD (F) after the biofix date. Egg-laying will begin at 974 GDD(F) after the biofix date, with the first egg-hatch/ larvae at 1069 GDD (F) and pupation begins at 1431 GDD(F) after the biofix date.

Sources:

AliNiazee, M. T. 1979. A computerized phenology model for predicting biological events of Rhagoletis indifferens (Diptera: Tephritidae). Can. Ent. 111: 1101-1109.