Degree Days

Note: SIR will no longer be uploading degree days to our website. For current degree day information and models please access the BC Decision Aid System (DAS) below. If you are unable to access DAS or require additional help, please contact SIR directly at 1-800-363-6684.

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 Days Predict When Codling Moths are Flying and When Eggs are Hatching

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 degreedays to predict codling moth development. These predictions are summarized in this table. These predictions are useful to manage this pest.

Degree day total
(+/- 3-5 DD)
Codling moth stage of development
100Emergence of 1st brood moths from overwintering larvae
150Beginning of 1st brood egg laying
220Start of 1st egg hatch (first brood larvae)
500End of emergence of 1st brood moths
575Start of emergence of 2nd brood moths
650End of 1st brood egg hatch
700Start of 2nd brood egg hatch (2nd brood larvae)
1140End of 2nd brood moth emergence
1160Start of 3rd brood moth emergence
1275End of 2nd brood egg hatch
1300Start of 3rd brood egg hatch

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 Days on the Decision Aid System Website

The most reliable, and up-to-date Degree Day totals can be found online at URL:

This website provides degree day information in a user friendly way. This website can help you determine what life stage the codling moth is in, when to spray with which product, and how the spray you select will affect beneficial insects. This website can also help you evaluate the effectiveness of the sprays you put on this season (or last) and help you determine if/when to spray next.  It also provides provides guidance on how weather affects your trap counts. A suite of pest, disease, and horticultural models are available free of charge on the Decision Aid Website  to help you with your farming practices.

If you are unable to access the Degree Days on this website or would like help setting up a free account, please contact SIR directly at 1-800-363-6684.