The Oriental Fruit Moth (Grapholita molesta) is an important pest on nuts and fruits in some areas. Overwintered Oriental Fruit Moth larvae typically emerge in late winter/ early spring and the first adults may be seen soon after. There can be as many as 5-6 generations in a year, depending on the weather. Insecticide treatments targeting 1st or 2nd generation larvae are typically the best way to control Oriental Fruit Moth populations for the entire growing season. The Oriental Fruit Moth Growing Degree Day Model, developed by researchers, 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 
Oriental Fruit 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 86F. 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 approximately 201 GDD(F). The next generation of adults will emerge at approximately 966 GDD(F).

Adjusting Biofix for Each Generation

For best results in second generation of Oriental Fruit Moths in a given season, the biofix should be reset when new pheromone traps have successfully capture adult moths in late spring/ early summer.

Source:

Croft, B. A., M. F. Michels, and R. E. Rice. 1980. Validation of a PETE timing model for the oriental fruit moth in Michigan and central California (Lepidoptera: Olethreutidae). Great Lakes Entomol. 13: 211-217.