WSU Extension

Hortsense

Caption: Apple ermine moth
Photo by: A.L. Antonelli
  
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Apple : Apple ermine moth
(revision date: 2/14/2019)


Biology
The apple ermine moth is an imported pest which feeds exclusively on apples. The adult moth has silver-white wings spotted with black. Larvae are gray, cream-colored, or greenish with dark spots along the sides. They may reach 3/4" long at maturity. Young larvae feed on developing leaves, mining out leaf tissues. They later move into the foliage and feed as tent caterpillars. Several leaves are tied together with webbing to make nests up to 3" across. Each nest contains several caterpillars. New nests are made as leaves in old ones are consumed. The caterpillars pupate in clusters within webbing, beginning around June. Adults emerge from late June onward, with females laying eggs into the fall. Egg masses are about 1/2" across and are found on the bark. They are initially yellow but age to red then gray in color.
Management Options

Non-Chemical Management
  • Prune out and destroy nests (in May) when practical. Also remove any pupating clusters when noticed.
  • Pick off or prune out any egg masses observed on the bark in the fall.
Select non-chemical management options as your first choice!

Chemical Management


See label for instructions. Apply Bt only when caterpillars are feeding. Use a spreader-sticker with liquid Bt formulations. Esfenvalerate is toxic to bees. Do not apply products containing esfenvalerate on or near blooming plants. To minimize risk to bees, apply in the evening after bees have stopped foraging for the day. Homeowners should not make foliar applications to trees over 10 ft tall. Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Captain Jack's Deadbug Brew R-T-U [Organic]
    Active ingredient: spinosad (spinosyn A+D)  |  EPA reg no: 4-472
  • Bonide Thuricide BT Conc
    Active ingredient: Bacillus thuringiensis subsp. kurstaki  |  EPA reg no: 4-226
  • Bull's-Eye Bioinsecticide
    Active ingredient: spinosad (spinosyn A+D)  |  EPA reg no: 62719-314-56872
  • Monterey Bug Buster II
    Active ingredient: esfenvalerate  |  EPA reg no: 1021-1778-54705
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • This list may not include all products registered for this use.
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Caption: Apple ermine moth
Photo by: A.L. Antonelli