Indianmeal Moth

The Indianmeal Moth (Plodia interpunctella) is pest which can leave its eggs on food products, but it can also effect almonds, pistachio or walnuts.

The Indianmeal Moth Growing Degree Day Model, developed by researchers, and available on the Pest Prophet app, is a tool growers can use to predict emergence of 2nd generation adults which can be targeted by insecticide or pheromone treatments or for trapping.

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 Indianmeal Moths, this biofix is the first date of consistent, sustained adult moth catches, or observations, using pheromone traps in the orchard. 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, however, researchers have found that the Indianmeal Moth has different growth rates depending on its host. For Bran, growing degree days may be calculated using a lower threshold of 16.6 C and an upper threshold of 35C. This can be done using daily high and low temperatures, or using hourly temperature data using the Pest Prophet app. The next generation of adults will emerge at approximately 268 GDD(C).

For Almonds, the lower threshold is 17C, and adults emerge at 344 GDD (C).

For Pistachios, the lower threshold is 17.1 C, and adults emerge at 358 GDD (C).

For Walnuts, the lower threshold is 18 C, and adults emerge at 402 GDD (C).

All these models are available on the Pest Prophet app.

Adjusting Biofix for Each Generation

For best results in second generation of Indianmeal 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:

Johnson, J. A., P. L. Wofford, and L. C. Whitehand. 1992. Effect of diet and temperature on development rates, survival, and reproduction of the Indianmeal moth (Lepidoptera: Pyralidae). J. Econ. Entomol. 85: 561-566.