The Silver Y Moth (Autographa gramma) is a migratory butterfly. Researchers at Oregon State University have developed a growing degree day model for Silver Y Moth to help predict when different life cycle stages will occur, which is helpful for observing the Silver Y Moth.

Calculating Growing Degree Day Units

The Silver Y Moth growing degree day model uses a lower threshold of 48F and an upper threshold of 95F 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 Silver Y Moth model, the biofix date should be set to Jan. 1st for the Northern Hemisphere, in order to predict the emergence of adults from overwintered larvae, and the following generations. Approximately 361 GDD(F) after the Jan. 1st biofix date the first adults from overwintered larvae will be observed.

Sources:

Honěk, A., V. Jarošík, Z. Martinková, and I. Novák. 2002. Food induced variation of thermal constants of development and growth of Autographa gamma (Lepidoptera: Noctuidae) larvae. European Journal of Entomology. 99:241-252