The Codling Moth (Cydia pomonella) is an important pest on apples and other fruit in California, the Pacific Northwest, and other locations. Overwintered Codling Moth larvae typically emerge in late winter/ early spring and the first adults may be seen soon after. There can be 3-4 generations in a year, depending on the weather. Mating disruption through pheromones, targeting adult moths is the most commonly used technique to control Codling Moths in California and the Pacific Northwest. The Codling Moth Growing Degree Day Model, developed by researchers at the USDA, 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 Codling Moths, this biofix is the first date of consistent, sustained adult moth catches using pheromone traps in the orchard or vineyard. Traps should be placed in early spring, or late winter, and checked on a regular basis. Once adult moths have been 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 50F and an upper threshold of 88F. This can be done using daily high and low temperatures, or using hourly temperature data using the Pest Prophet app. The first egg hatch will occur at about 221 GDD (F) and peak at approximately 656 GDD. Adult moth Ffight for the second generation will begin at approximately 920 GDD after the biofix date. The thrid generation will begin adult moth flight at approximately 1940 GDD after the first biofix. Traps and mating disruption pheromones should be placed to coincide with adult moth flight stages.

Adjusting Biofix for Each Generation

For best results after the second generation of Codling moths in a given season, the biofix should be reset when new pheromone traps have successfully capture adult moths in late spring/ early summer.  Trap placement and treatments should then coincide with the first generation of adults, following the adjusted biofix date. This will be improve accuracy of later life cycle stage predictions.

Source:

Knight, A.L. 2007. Adjusting the phenology model of codling moth (Lepidoptera: Tortricidae) in Washington state apple orchards. Environmental Entomology 36:1485-1493