The Mint Flea Beetle (Longitarsus waterhousei) is an important pest on peppermint in some areas. They can be very challenging to control, and different insecticide products may target different life cycle stages (eggs, nymphs, adults) and not affect the pest at the other life cycle stages. For this reason, predicting when different life cycle stages will occur, based on current observations and weather data, can be very helpful. Researchers have developed a growing degree day model for Mint Flea Beetle to help predict when different life cycle stages will occur.

Calculating Growing Degree Day Units

The Mint Flea Beetle growing degree day model uses a lower threshold of 41F and an upper threshold of 103F for calculating growing degree day units. The growing degree day units can be calculated from daily maximum and minimum temperatures using these thresholds, or by using the Pest Prophet app, which features this model and is easy to set up and use.

Setting the Biofix date

In order to begin growing degree day accumulation, first a “biofix” date must be set which is the first date, after which growing degree day units will begin to accumulate. In the Pest Prophet app, the biofix date can be adjusted for any observed life cycle stages. For the Mint Flea Beetle model, the biofix date should be set when the first generation of adults, or eggs are observed. Approximately 405 GDD(F) after the biofix date (when eggs are observed), first instar larvae will be observed. The model can be used to track progression through different instars and pupation. At approximately 1475 GDD (F) the next generation of adults will be observed.

Sources:

Berry et al. 2000. Mint Flea Beetle Growing Degree Day model