How to Manage Pests

California Sunset Temperatures for Codling Moth Monitoring

Purpose of temperature display

Pheromone traps, degree-days, and sunset temperatures are used to determine egg hatch and proper spray timing for control of codling moth. In spring, degree-days should be accumulated from the first date that moths are consistently found in traps and when sunset temperatures have reached 62ºF. This date is the first biofix, and is used in conjunction with accumulated degree-days to time sprays for effective control of the different generations of codling moth.

For more information, see:

• UC Pest Management Guidelines for apples, pears, walnuts, prunes, plums, and home & landscape
• Degree-day calculator for codling moth
• About degree-days and phenology models

About the temperature data

The temperatures are from stations that are a part of the Department of Water Resources California Irrigation Management Information System (CIMIS) network. These stations are located throughout the state, and most are in rural areas. The temperature sensor is shielded from the sun and rain, mounted at 1.5 m, and hourly averages for each hour of the day are reported soon after midnight.

The sunset temperatures are available about 7 a.m. daily for the previous day. The temperatures are posted during March, April, and early May.

The same time of sunset is used for all locations in California, based on the actual time at Stockton. Minutes are rounded to the nearest hour. Since the moths fly for a few hours before and after sunset, the temperature at precisely sunset is not absolutely necessary, and this generalization has been used successfully for a number of years.