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Integrated Pest Management · Agriculture and Natural Resources

University of California

Using degree-days: Video tours

first degree-days video: using degree-days to time insecticide applications

Using degree-days to time insecticide applications in fruit and nut orchards.

second degree-days video: using UC IPM degree-day tools

Using UC IPM degree-day tools.
(View transcript.)

What are degree-days?

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.

Watch the first video to learn more about degree-days!

How are degree-days measured?

A good approximation of the degree-days accumulated for a pest can be calculated by knowing:

  • The identity and life cycle of the pest and the crop
  • When to start accumulating degree-days for a pest
  • The minimum and maximum temperatures at which the pest will develop
  • The highest and lowest temperatures in the field or orchard during pest development

Watch the second video to learn how to use the tools!

How do degree-day tools help with pest management?

  • Knowing what life stage the pests are at during a given day or week helps target control methods appropriately.
  • This helps avoid overspraying of pesticides by using them only when the pest is most sensitive to them.

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