The Potato Capsid (Closterotomus norvegicus) is a common pest on wide variety of hosts. 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 Potato Capsid to help predict when different life cycle stages will occur.

Calculating Growing Degree Day Units

The Potato Capsid growing degree day model uses a lower threshold of 43.5 F and an upper threshold of 93.3 F 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 Potato Capsid model, the biofix date should be set when the first generation of first instar nymphs are observed. 4th instar nymphs will occur at approximately 257 GDD(F), and 5th instar nymphs at 363 GDD (F). At approximately 479 GDD (F) after the biofix, the next generation of adults will be observed.

Sources:

Purcell, M., and S. C. Welter. 1990. A degree-day model for development of Calocoris norvegicus (Hemiptera: Miridae) and timing of management strategies.