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Codling Moth Monitoring in Idaho Report - 2026

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Codling Moth

Posted on: May 18, 2026 by Jemila Chellappa

Codling Moth Pest Alert

Idaho Orchard Monitoring Update

April-May 2026

Codling moth activity has now been detected across multiple regions of Idaho, with biofix dates established from April 20 through May 11, 2026. Monitoring efforts through the PNW Pest Alert Network and University of Idaho Extension indicate that codling moth emergence is progressing statewide, with earlier activity reported in southeastern and southwestern Idaho and later emergence occurring in northern and cooler production regions.

Biofix represents the first sustained moth capture in pheromone traps and serves as the starting point for Growing Degree Day (GDD) accumulation used to predict egg hatch and optimize management timing.

Reported Codling Moth Biofix Dates – Idaho 2026

What Growers Should Be Watching For

Adult codling moth flight is now underway in many Idaho orchard systems. Following biofix, degree-day accumulation becomes critical for predicting egg hatch and larval emergence. Under the standard codling moth model (50°F lower threshold; 88°F upper threshold), first egg hatch generally begins around 220–250 accumulated GDD after biofix.

Growers should:

• Continue checking pheromone traps weekly
• Begin tracking degree-day accumulations from local biofix dates
• Intensify scouting as egg hatch approaches
• Monitor fruit clusters and leaves for early larval activity
• Maintain orchard sanitation and remove infested fruit when possible

Why Biofix Matters

Codling moth development varies considerably across Idaho due to differences in elevation, temperature, and local climate conditions. Using local biofix dates and GDD accumulation provides more accurate timing for scouting and management than relying solely on calendar dates.

In warmer regions of southern Idaho, codling moth development may advance rapidly during warm weather periods. Cooler northern and higher-elevation areas may experience delayed development and later management windows.

Integrated Pest Management (IPM) Reminder

Effective codling moth management should combine:

• Pheromone trap monitoring
• Growing Degree Day models
• Field scouting
• Economic thresholds
• Timely management applications when necessary

Proper timing is essential because insecticide applications targeting newly hatched larvae are generally more effective than applications made after larvae enter the fruit.

Important Codling Moth GDD Benchmarks

Using the standard codling moth model:

• Lower threshold: 50°F
• Upper threshold: 88°F

Key biological events include:

• 100 DD: sustained adult flight increases
• 220–250 DD: first egg hatch begins
• 350 DD: peak early larval activity
• 500–600 DD: increasing first-generation pressure

$GDD=\frac{T_{max}+T_{min}}{2}-T_{base}$

What This Means Right Now

• Southern Idaho locations such as Boise and Twin Falls are likely already within the first egg hatch window and should intensify scouting and management timing.
• Southeastern Idaho sites like Malad and Montpelier are likely progressing into active larval emergence.
• Northern Idaho locations (Moscow, Sandpoint, Hope) are still earlier in codling moth development because of cooler spring temperatures.

The Boise monitoring site at Spaulding Ranch officially reported:

• Biofix: May 1
• Current accumulation: 262 DD (Base 50°F) as of May 8 

You can track live degree-day accumulation for each location directly through the PNW Pest Alert GDD Dashboard.

For codling moth management recommendations and spray timing guidance, consult the PNW Pest Management Handbook – Codling Moth Management in Apples.

Please continue submitting local codling moth observations and biofix information to support statewide monitoring and forecasting efforts through the PNW Pest Alert Network.