How to Predict Codling Moth Emergence in your Garden or Orchard

Codling Moth Adult
AJC1 from UK / CC BY-SA

For keen fruit tree gardeners, home orchardists and commercial orchards, accurately predicting Codling Moth emergence and when they start laying eggs is important. Due to recent warm weather in the BC Interior, Codling Moths are emerging and are about to start laying eggs. They should start emerging in Coastal BC in a couple of weeks depending on how warm it gets. Once they emerge, mating and then egg laying occurs when twilight temperatures are above 15°C. If you plan to protect your fruit with fruit sox or other barriers, they need to be in place before egg laying starts.

The codling moth, like all insects, is cold blooded. The temperature around it determines how fast it develops and how active it is as an adult moth. Degree days (DD) are a weather-based method to determine moth stage of development. One-degree-day results when the average temperature for a day is one degree over the threshold temperature which is 10°C for Codling Moths. Degree days to predict moth activity are accumulated on a daily basis starting on January 1st of each year.

Does this seem confusing? Read on for an easy way to work this out.

Pest Degree Day Calculator for British Columbia

BC Farmwest  has made a Perst Calculator to easily figure out Codling Moth Degree Days. This Pest Calculator can be used to determine degree days for several pests (including Codling Moths) at many locations across the province.

Here is how to use the calculator for Codling Moths at your location:

  • Set the pest to Codling Moths
  • Set the date range from January 1st to today
  • Set the location to the BC region where you live; and
  • Set the weather station to the closest geographic location to where you live

For example:

On May 9, 2020 the calculated Codling Moth Degree Days where I live in Langley are 26.2; this is well behind the 59 year average of  51.9 for this date

This type of Codling Moth Degree Day Calculation is called the No-Biofix-Model

Scroll to Top