Critical Time For Codling Moth Management

Written by Dani Gray, Tobin Northfield Washington State University, May 2026

What’s Happening Now in Washington

The season has been heating up fast, and codling moth has been blazing ahead. The first flight of codling moth is well underway across South Central Washington. During this time, keeping up with codling moth development through WSU’s Decision Aid System (DAS, https://decisionaid.systems/) is imperative, along with using lure baited traps to monitor for adult flight. It is also important to keep in mind the environmental differences, such as elevation, to stations you are monitoring and conditions in your own orchard. Some areas like, Finley (Finley Station, DAS), and Mattawa (AMT Station, DAS) are already reaching overwintering emergence predicted to be as high as 75% and egg hatch reaching 25% by May 11th according to the DAS codling moth model (estimations made May 7th), but other areas such as Radar Hill (Radar Hill Station, DAS), Royal City (Royal City.E Station, DAS), Red Mountain (Red Mtn Station, DAS), Moxee (Moxee.N Station, DAS), Toppenish (Toppenish Station, DAS), and Wapato (Wapato Station, DAS) all predicted to still be under 70% overwintering emergence and 15% egg hatch by May 11th. North of I90, in areas like Wenatchee (Wenatch. E Station, DAS), Brays Landing (Brays Landing Station, DAS), Orondo (Orondo Station, DAS), Brewster (Brewster.S Station, DAS) and Cashmere (Cashmere Station, DAS) all expected to be under 10% egg hatch by May 11th. On the far North end of the state in Ellisford (Ellisford Station, DAS and Loomis.Grd Station, DAS), Oroville (Oroville Station, DAS), and Okanogan, these areas are just entering egg hatch and predicted to be under 4% egg hatch by May 11th.

Starting The Season Strong

Management of the first generation of codling moth is critical because it sets the tone for the entire season. When control slips early, populations compound across generations – leading to hotspots, fruit injury, increased sprays and labor costs, and increased resistance risk due to greater pesticide exposure. The number of codling moth will multiply greatly each generation if no action is taken, as a single female can lay on average 50 eggs – this is also why mating disruption is a critical foundation for codling moth management, because we can reduce this number significantly for each day mating is delayed (Ferro et al., 1975, Jones & Wiman, 2012). When the first generation is well controlled and populations stay low, tools like mating disruption, insecticides, and cultural controls also all work more effectively. Simply put: managing the first generation right makes the rest of the season easier; missing it means chasing codling moth all year.

Timing of management decisions is one of the most important factors for managing codling moth – nobody wants to see a pesticide application miss its target window. This is especially critical at the start of a generation, as most larval insecticides rely on contact or ingestion by the larvae in the short period between egg hatch and entering the apple. This makes predicting the interval between egg lay and egg hatch critical for ovicide and larvicide applications. While a Larvicide Only program is an option, WSU recommends a Delayed Cover approach, especially in the first generation. A Delayed Cover program for codling moth uses an early ovicide application, which can be either a residual or topical ovicide but used at different timings (see Table. 1), allowing the first larvicide spray to be applied later in the season after effectively controlling that generation at the egg stage with ovicides. Targeting this early stage reduces and delays larval pressure, allowing larvicides to be applied later when they are most effective. This spreads control across life stages, improving overall pressure and reducing risk and resistance pressure. Timings and recommend spray program strategies can be found in Table 1.

Table 1. Codling moth spray programs and associated timings with insect development. See bottom of table for important footnotes.

Footnotes
*Conventional programs assume 2 larvicide applications per generation; additional larvicide applications might be required and should be based on codling moth capture in monitoring traps exceeding thresholds
** A list of organic and conventional ovicides and larvicides can be found in the WSU Crop Protection Guide https://cpg.treefruit.wsu.edu/
*** WSU Decision Aid System https://decisionaid.systems/
**** In the first generation, degree day development is slower, making it easier to apply residual or topical ovicides during their target window. In generations after, degree development speeds up dramatically, making it more difficult to discreetly target start of egg lay and start of egg hatch.
***** Avoid excessive use of oil or under conditions that pose a high risk of phytotoxicity. These conditions include but are not limited to: 48 hours before or after freezing temperatures, when temperature exceeds 85°F (29°C) during or shortly after application, applying sulfur or Captan during or within 2 weeks of an oil application, or other stress conditions (water stress, cold or frost injury, or other mechanical injury).

Contact

Dani Gray
Washington State University, Tree Fruit Extension
IPM Extension Educator
Danielle.gray@wsu.edu
509-542-7842

References

Washington State University. Decision Aid System. https://decisionaid.systems/ (Accessed May 7, 2026).