What are degree days?

Growing degree days (DD) are a weather-based indicator for assessing crop and pest development. It is a calculation used by crop producers that measures heat accumulation used to predict plant and pest development rates. Growing degrees are defined as the mean daily temperature (average of daily maximum and minimum temperatures) above a certain threshold base temperature accumulated on a daily basis over a period of time. Daily growing degree day values are added together from the beginning of the season. Degree day totals are also used for comparing the progress of a growing season to the long-term average.

Degree Day Development Table

The codling moth, like all insects, is cold blooded. Meaning, the temperature around it determines how fast it grows and how active it is as an adult moth. We can take advantage of this to predict what life stage the majority of the codling moths population are in. Scientists have developed a model that uses degree–days to predict codling moth development. These predictions are summarized in this table.

A complete codling moth degree day development table is also available as a PDF – Full Codling Moth Degree Day Development Table.

More information about the codling moth stages of development, see Codling Moth.

Degree Day Tables

The degree day totals in the table below indicate the predicted stage of development of codling moth populations near specific weather stations located around the valley. Growers and advisors can use the values to determine the life stages of the codling moth in their area. This will help determine the proper time to apply ovicidal and larvicidal products to control each of the codling moth generations if needed.