At a Glance
- Apple clearwing moth (ACWM) is an invasive trunk‑boring pest of apple trees.
- Larvae feed beneath the bark, weakening trees and contributing to decline.
- Trunk sprays are one of the most effective control options.
- Optimal timing occurs between 150 and 200 degree‑days (DDC).
- Trunk spray timing can be tracked using the BC DAS Codling Moth model.
Why Is Apple Clearwing Moth a Problem?
Apple clearwing moth larvae bore into the trunks of apple trees, where they feed beneath the bark. This feeding disrupts nutrient transport and can weaken trees over time, particularly in young or stressed blocks. Because larvae are protected inside the tree, surface sprays are often ineffective once infestations are established.
Trunk Spray Timing
Trunk sprays are one of the most effective applications for managing apple clearwing moth. Applications should be timed to target larvae early:
- Begin applications at 150 DDC
- Aim to complete sprays by 200 DDC
Growers can use the Codling Moth degree‑day model in BC DAS to time trunk sprays accurately.
Field research has shown that high‑volume trunk applications are most effective. Spray to runoff using high‑volume gun sprays, with up to 800 litres per acre, to ensure thorough trunk coverage.
Product Options
- Conventional: Apply Rimon at 1.4 L per 1000 L of water. Research indicates Rimon can kill larvae already present in the tree.
- Organic: Entrust is available for organic production systems.
Local research by Dr. Gary Judd, along with consultants Linda Edwards and Tamara Richardson, has shown that trunk sprays using Rimon (or Entrust in organic systems) are likely the single most effective control measure for apple clearwing moth.
Scouting
Scout blocks by examining tree trunks for reddish‑brown frass emerging from entry holes. Frass may also be found around:
- Aerial roots
- Pruning scars
- Branch collars
- Graft unions
Infestations may also occur in the upper canopy at pruning wounds. Pay particular attention to weak or declining trees, which are often more susceptible.
Additional Summer Protection
In young blocks, additional summer sprays may be needed to prevent new damage. Two sprays are generally recommended at:
- 550 degree‑days
- 850 degree‑days
Degree‑day timing is based on the BC DAS Codling Moth model. Local experience indicates this model works well for apple clearwing moth when daytime temperatures remain below 30 °C. For more information, check out the Tree Fruit Production Guide.