Honeylocust Borer

    Honeylocust Borer

    Agrilus difficilis 

    honeylocust borer

    Honeylocust borer (Kansas Department of Agriculture, Bugwood.org)

    honeylocust borer larva

    Emerald ash borer larva, similar in appearance to honeylocust borer larva (Pennsylvania Department of Conservation and Natural Resources, Bugwood.org)

    honeylocust borer damage

    Honeylocust borer damage (Ryan Davis, Utah State University Extension)

    Pest Description

    • adults: 1/4 – 3/4 inch; slender, black with greenish-purple reflections
    • beetle with yellow spots on abdomen below the wings
    • larvae: creamy white with an enlarged head area; tapeworm-like appearance

    Host Plants, Diet & Damage

    • honeylocust
    • feed on phloem and etch sapwood of main trunk or branches \
    • affect damaged areas of honeylocust bark, especially sun-scalded areas
    • wet areas on bark and oozing from bore holes
    • create serpentine galleries under the bark
    • leave diagnostic, D-shaped exit holes in bark
    • can cause canopy dieback or rarely complete tree death
    • trees attacked by this insect are usually in poor condition, damaged, or grown in harsh hardscapes

    Biology, Life Cycle & Damaging Life Stage

    • overwinter as larvae under the bark or in the sapwood
    • adults present late-May through September
    • eggs laid singly or in groups under bark flaps
    • one generation per year
    • prefer stressed, weakened trees
    • larvae are the damaging stage

    IPM Recommendations

    • Keep trees well watered.
    • Plant in sites that minimize stress on honeylocust.
    • Prevent mechanical or environmental injury to trees.
    • Apply an insecticide (carbamate; pyrethroid) to bark of stressed or injured trees prior to and during peak beetle flight.