Using Degree-days to Time Insecticide Applications in Fruit and Nut Orchards

Invertebrates, including insect pests, require a certain amount of heat to develop from one stage to another in their life cycle (for example, from egg to larva). The total amount of heat required to develop from one stage to another is calculated in units called degree-days (DD). If the average temperature in 24 hours is one degree higher than the minimum temperature required for a particular pest, one degree-day is accumulated. Accumulating degree-days helps you time a treatment to when the pest is at its most vulnerable stage.