WSU Extension

Hortsense

Filbert : Filbertworm
(revision date: 3/10/2017)


Biology
The filbertworm is the larval stage of a gray to reddish moth. The adult moth has copper- to gold-colored bands across the forewings and a wingspread of approximately 1/2". The female moth lays eggs on or near the developing nut. Emerging caterpillars bore into the nut through the base of the husk. The caterpillars feed inside the nut, blackening and destroying the kernel. Mature caterpillars are pinkish to white and 1/2"-3/4" long. They feed for three or four weeks before dropping to the ground to pupate.
Management Options

Non-Chemical Management
  • Harvest nuts as early as possible. Dry nuts immediately after harvest to minimize damage.
Select non-chemical management options as your first choice!

Chemical Management

Apply in early July and again 3 weeks later. NOTE: 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.
  • Bug Buster-O [Organic]
    Active ingredient: pyrethrins  |  EPA reg no: 1021-1771-54705
  • Monterey Bug Buster II
    Active ingredient: esfenvalerate  |  EPA reg no: 1021-1778-54705
  • This list may not include all products registered for this use.
Images
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Caption: Nut damaged by filbertworm larva
Photo by: K. Grey
Caption: Filbertworm larva
Photo by: K. Grey
Caption: Pupa and cacoon
Photo by: K. Grey
Caption: Adult
Photo by: K. Grey
Caption: Larval exit hole to filbert nut
Photo by: K. Grey