Apple: Apple ermine moth

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

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

• 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.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

• 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.

Approved Pesticides

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 registration number: 4-472]
• Bonide Thuricide BT Concentrate
  Active ingredient: Bacillus thuringiensis subsp. kurstaki [EPA registration number: 4-226]
• Monterey Bug Buster II
  Active ingredient: esfenvalerate [EPA registration number: 1021-1778-54705]
• Safer Brand BioNEEM Multi-Purpose Insecticide and Repellent Concentrate [Organic]
  Active ingredient: azadirachtin [EPA registration number: 70051-6-42697]
• This list may not include all products registered for this use.