Filbertworm Moth

Filbertworm (Cydia latiferreana) is a common pest on hazelnut in the Pacific Northwest and other regions. They can be very challenging to control, and different insecticide products may target different life cycle stages (eggs, nymphs, adults) and not affect the pest at the other life cycle stages. For this reason, predicting when different life cycle stages will occur, based on current observations and weather data, can be very helpful. Researchers have developed a growing degree day model for Filbertworm to help predict when different life cycle stages will occur.

Calculating Growing Degree Day Units

The FIlbertworm growing degree day model uses a lower threshold of 50F and an upper threshold of 110F for calculating growing degree day units. The growing degree day units can be calculated from daily maximum and minimum temperatures using these thresholds, or by using the Pest Prophet app, which features this model and is easy to set up and use.

Setting the Biofix date

In order to begin growing degree day accumulation, first a “biofix” date must be set which is the first date, after which growing degree day units will begin to accumulate. In the Pest Prophet app, the biofix date can be adjusted for any observed life cycle stages.

For the Filbertworm model, the biofix date should be set to April 1st for the Northern Hemisphere, in order to predict the emergence of adults from overwintered larvae, and the following generations. Approximately 580 GDD(F) after the April 1 biofix date the first adults from overwintered larvae will be observed. Peak egg hatch and larvae found in nuts will occur at approximately 1023 GDD(F). Approximately 1188 GDD(C) after the biofix date, the next generation of Adult moths will emerge.

For best results the biofix should be re-adjusted for each generation, based on scouting observations. This will improve accuracy of later crop stage predictions.

Sources:

AliNiazee, M. T. 1983. A Degree-Day Method for Predicting the Filbertworm Emergence. Proc. Nut Growers Soc. of Oreg. Wash and Brit. Columbia. Vol. 68:37-39.