Pest Degree Days to Predict Insect Development

Temperature plays a major role in the growth and development of insects. There is a threshold temperature for each insect where no development occurs when temperatures are below that level and a maximum temperature (termed upper cutoff) above which development stops. In between is an optimum temperature range in which insects grow rapidly. These temperatures can be used to predict insect activity.

Degree days are used to predict insect development. One degree day results when the average temperature for a day is one degree over the threshold temperature. The Farmwest website maintains a Pest Calculator that calculates degree days for several pests at many locations across the province.  Currently you can monitor degree days for Apple Clearwing Moth, Codling Moth, Leaf rollers, fruit flys and more.

Following degree days will allow you to become more accurate in your pest management. This in turn can result in reductions in pesticide use and better control through more accurate timing when pesticides are required.