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Pacific Northwest Pest Alert Network – 25 Year Celebration Reminder!
All Crops Eastern Idaho, Magic Valley, Treasure Valley, Treasure Valley - Idaho, Northern Idaho, Treasure Valley Oregon
Posted on: May 19, 2026 by Jemila Chellappa
Codling Moth Monitoring in Idaho Report - 2026
All Crops Eastern Idaho, Magic Valley, Treasure Valley, Treasure Valley - Idaho, Northern Idaho, Treasure Valley Oregon
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
| Location | Biofix Date | |
|---|---|---|
| Malad (83252) | April 20 | |
| Montpelier (83254) | April 20 | |
| Pocatello (83201) | April 24 | |
| Boise (Spaulding Ranch) | May 1 | |
| Twin Falls | May 2 | |
| Moscow (83843) | May 6 | |
| Sandpoint | May 8 | |
| Hope | May 10 | |
| Menan | May 11 |
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
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.
First codling moth flight of 2026 (biofix) detected in Latah County
All Crops All Locations
Codling Moth
Posted on: May 16, 2026 by Samuel DeGrey
Multiple codling moths were captured in a monitoring trap in Moscow, Latah County, Idaho on May 6th, 2026.
The first detected flight date of May 6th will
serve as the biofix, or the date where we begin accumulating degree
days, for Moscow, Idaho. Degree days provide an estimate for life cycle
stages of insect pests, and can be a tool to better time management
decisions for farmers, horticultural professionals, and gardeners.
Please visit our degree day dashboard to track degree days for codling moth in Moscow - https://pnwpestalert.net/gdd/index
Please consult the Pacific Northwest Pest Management handbook for degree-day based management recommendations for codling moth - https://pnwhandbooks.org/insect/tree-fruit/apple/apple-codling-moth .
2026 Miller Research Potato Pest Management Field Day
Potato All Locations
Posted on: May 14, 2026 by Jeff Miller
Miller Research will be holding its annual potato pest management field day on Thursday, August 20. The field day will begin at the Miller Research main office at 422 E 200 N, Rupert (42.648994 N, 113.585612 W).
The cost to attend is $20 and payment can be made online through PayPal or at the event. Contact Cheryn Suarez at cheryn@millerresearch.com or (208) 312-4650 if you have questions.
The presentations will focus on chemical management of diseases and will highlight research that has been funded by the Pacific Northwest Potato Research Consortium. ISDA pesticide recertification credits and CCA Pest Management credits will be requested for this meeting.
Topics will include:
Alternatives to Metam for Verticillium control
Display of powdery scab symptoms on different varieties – research on PMTV
Performance of fungicide programs for foliar disease management
Black dot management on stems and tubers
Long-term soil health project (fumigation, compost, green manure)
Lunch will be provided at the conclusion of the meeting.
» https://millerresearch.com/event/2026-miller-research-potato-pest-management-field-day/
Cereal Leaf Beetle Alert in Small Grains
All Crops Eastern Idaho, Magic Valley, Treasure Valley, Treasure Valley - Idaho, Northern Idaho, Treasure Valley Oregon
Cereal Leaf Beetle
Posted on: May 14, 2026 by Jemila Chellappa
Have You Noticed Black, Slimy Smears on Your Cereal Leaves?
Payette County – New Plymouth Area
University of Idaho Extension is receiving reports of cereal leaf beetle (CLB) activity in winter cereals near New Plymouth in Payette County.
Growers and crop advisors are encouraged to scout wheat, barley, oats, and other small grain fields for signs of feeding injury, especially as crops are already facing multiple stresses this season including drought, freeze injury, BYDV, mites, and eyespot.
What Does Cereal Leaf Beetle Damage Look Like?
One of the most recognizable signs of cereal leaf beetle larvae is the appearance of:
- Black, slimy, feces-covered larvae on leaves
- “Smeared” or slug-like appearance on foliage
- Long, narrow feeding scars or “windowpane” injury between leaf veins
- Skeletonized leaf tissue, especially on upper leaves
The larvae cover themselves with fecal material, giving them a shiny black or slimy appearance that can easily be mistaken for disease or dirt.
Adult beetles are small with:
- Metallic blue-black wing covers
- Red-orange thorax and legs
Why Is This Important This Year?
Small grains across Idaho are already under severe stress from:
- Warm winter conditions
- Drought stress
- Freeze and frost injury
- BYDV and aphid pressure
- Mite infestations
- Eyespot and other diseases
Additional feeding from cereal leaf beetle larvae can further reduce photosynthetic area and weaken already stressed plants, particularly during flag leaf and heading stages.
The flag leaf contributes significantly to grain fill, making protection of upper canopy leaves especially important.
What to Scout For
Check:
- Upper leaf surfaces for larvae and feeding scars
- Field edges first
- Thin or stressed areas of the field
- Areas with lush growth or volunteer cereals nearby
Larvae are often easiest to spot in the morning or cooler parts of the day.
Management Considerations
Management decisions should be based on:
- Crop growth stage
- Level of feeding injury
- Presence of larvae
- Overall crop condition and yield potential
In severely drought- or freeze-stressed fields, economic return from treatment may be limited.
Natural enemies such as parasitoid wasps can also help suppress cereal leaf beetle populations, so unnecessary insecticide applications should be avoided when possible.
Look into the Pacific Northwest Insect Management Handbook or contact your local Extension educator for current treatment thresholds and labeled management options.
What You Can Do Now
- Scout fields regularly over the next 1–2 weeks
- Document feeding severity
- Monitor flag leaf injury
- Consider overall crop stress before making treatment decisions
- Reach out to Extension if you observe significant infestations
If you are seeing unusual injury patterns or suspect cereal leaf beetle activity in your area, please report observations to your local University of Idaho Extension office.
For more information on cereal leaf beetle management:
- Pacific Northwest Pest Management Handbook
- University of Idaho Extension resources
- PNW Pest Alert Network
Stay safe and continue scouting carefully this season.
Contact for Assistance - Jemila Chellappa, Area Extension Educator - Cropping Systems, Southern District, UI Extension jemila@uidaho.edu/208-459-6003
» https://pnwhandbooks.org/insect/agronomic/small-grain/small-grain-cereal-leaf-beetle
Pest Alert: Cutworm Activity Observed in Alfalfa Fields
All Crops Eastern Idaho, Magic Valley, Treasure Valley, Treasure Valley - Idaho, Northern Idaho, Treasure Valley Oregon
Cutworm
Posted on: May 14, 2026 by Jemila Chellappa
Severe cutworm feeding has recently been reported in alfalfa fields in Southwest Idaho. Growers are encouraged to scout fields carefully, especially during evening or early morning hours when larvae are most active.
What to Look For
Cutworm larvae feed on stems and crowns, often cutting young shoots near the soil surface. Damage may appear as:
- Wilted or clipped stems
- Thinning patches in the field
- Reduced regrowth
- Irregular feeding injury near the crowns and lower stems
Larvae are typically found hiding in soil cracks, under residue, or near the base of plants during the day.
Understanding the Life Cycle
Cutworms are the larval stage of moths. The damaging caterpillar stage generally lasts several weeks before larvae pupate in the soil and emerge as moths. Once pupation occurs, feeding stops.
In many Idaho alfalfa systems:
- Cutworm outbreaks are often most severe during spring and early summer.
- Large larvae may be nearing the end of their feeding period.
- Some species can produce multiple generations, but damaging populations are not always present throughout the entire summer.
Field Scouting Recommendations
Growers should:
- Check multiple locations across the field
- Count larvae per square foot
- Determine whether larvae are small and actively feeding or nearly mature
- Evaluate regrowth after cutting
Fields approaching harvest may benefit from timely cutting, which can reduce feeding pressure and expose larvae to predators and environmental stress.
Management Considerations
Treatment decisions should be based on:
- Severity of stand loss
- Larval size and density
- Crop growth stage
- Ability of the stand to recover after harvest
Established alfalfa stands can sometimes recover if feeding pressure declines quickly. However, continued feeding on regrowth or crown injury may justify additional management actions. For insecticide options, economic thresholds, and additional integrated pest management recommendations, consult the PNW Insect Management Handbook – Alfalfa Insect Management Section.
Continue monitoring fields closely over the next several weeks, particularly where heavy feeding has already been observed.
» https://pnwhandbooks.org/insect/hay-pasture/alfalfa/alfalfa-hay-cutworm
» https://pnwhandbooks.org/insect/legume-grass-field-seed/alfalfa/alfalfa-seed-cutworm
