Walnut Husk Fly

    Walnut Husk Fly

    Walnut husk fly adult on a sticky trap. Walnut husk fly adult on a trap.

    Walnut husk fly larva.
    Walnut husk fly larva.

    HOSTS

    • Walnut
    • Apricot
    • Peach/Nectarine

    DESCRIPTION

    The walnut husk fly is related to the western cherry fruit fly. The adults are about the size of a house fly and have patterned wings with an inverted “V” at the tip. It lays eggs in the husk of walnut after the husk has softened a bit. It will also lay its eggs in softening peach and nectarine fruits, especially where husk fly numbers are elevated due to the presence of non-treated walnut trees. Larvae (maggots) feed within fruits.

    BIOLOGY

    The walnut husk fly is a tephritid fruit fly like the apple maggot and western cherry fruit fly. It overwinters as a pupa in the soil under trees that were infested. Adult flies start to emerge in early to mid summer, and continue through October. Females lay eggs under the skin of walnuts, peach, nectarine, or apricot. Maggots feed until maturity and then drop to the soil to pupate.

    SYMPTOMS

    • Small maggots inside peach/nectarine or apricot fruit. There may also be holes in fruit
    • Blackened or shriveled walnuts

    GENERAL MANAGEMENT

    Treat by 7-10 days after the first adult flies are caught or beginning in mid to late July (in northern Utah) using carbaryl, malathin, or spinosad.

    Monitoring:

    Adults can be monitored with Pherocon AM® (yellow sticky) traps baited with ammonium carbonate.

    Insecticides:

    • Residential: spinosad°, carbaryl, malathion, pyrethrin°, or gamma-cyhalothrin (one or two sprays may be needed)
    • Commercial: click here

    Precautionary Statement: Utah State University and its employees are not responsible for the use, misuse, or damage caused by application or misapplication of products or information mentioned in this document. All pesticides are labeled with ingredients, instructions, and risks, and not all are registered for edible crops. “Restricted use” pesticides may only be applied by a licensed applicator. The pesticide applicator is legally responsible for proper use. USU makes no endorsement of the products listed in this publication.