The Fruittree Leafroller Moth (Archips argyrospila) is an important pest a variety of tree hosts. Overwintered Fruittree Leafroller larvae typically emerge in late winter/ early spring and the first adults may be seen soon after. There can be 2 generations in a year, depending on the weather. Insecticide treatments targeting 1st or 2nd generation larvae are typically the best way to control Fruittree Leafroller populations for the entire growing season. The Fruittree Leafroller 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 
Fruittree Leafrollers, this biofix is the first date of consistent, sustained adult moth catches using pheromone traps in the field. 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 41F and an upper threshold of 82F. This can be done using daily high and low temperatures, or using hourly temperature data using the Pest Prophet app. The the larval stage will be between after approximately 278GDD (F). The optimum timing for a single insecticide treatment is after this event.

Adjusting Biofix for Each Generation

For best results in second generation of Fruittree Leafrollers in a given season, the biofix should be reset when new pheromone traps have successfully capture adult moths in late spring/ early summer. Approximately after 278 GDD(F) following the readjusted biofix is, again, the optimum time for insecticide treatment.

Source:

Judd, G. J. R., M. G. T. Gardner, and D. R. Thomson. 1993. Temperature-dependent development and prediction of hatch of overwintered eggs of the fruittree leafroller, Archips argyrospilus(Walker) (Lepidoptera: Tortricidae). Can. Entomol. 125: 945-956.