The Diamondback Moth (Plutella xylostella is a widespread pest, seen wherever cabbage, and other cole crops, are grown. Overwintered Diamondback Moth larvae typically emerge in late winter/ early spring and the first adults may be seen soon after. There can be many generations in a year, depending on the weather. Insecticide, or Bacillus thuringeiensis treatments targeting larvae are typically the best way to control Diamondback Moth populations for the entire growing season.

The Diamondback Moth Growing Degree Day Model, developed by researchers at Cornell University, and available on the Pest Prophet app, is a tool growers can use to predict egg hatch based on adult trap catches and field-specific temperature data.

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 Diamondback Moths, this biofix is the first date of consistent adult moth observations, or trap catches. Once adult moths have been seen, or trapped, for a few weeks in a row, the date of the first catch should be used as the biofix.

Growing Degree Day Accumulation and Treatment

After the biofix is set, growing degree day accumulation can begin, using a lower threshold of 45.1F. This can be done using daily high and low temperatures, or using hourly temperature data using the Pest Prophet app. The next generation will occur at approximately 509 GDD (F) after adult moth catch.

For best results in second generation of Diamondback moths in a given season, the biofix should be reset for each subsequent generation.

Source:

Harcourt, D. G. 1954. The biology and ecology of the diamondback moth, Plutella maculipennis (Curtis), in eastern Ontario. Ph.D. thesis, Cornell University, Ithaca, N.Y. 107p.