Locust Borer

    Locust Borer

    Megacyllene robiniae

    locust borer

    Locust borer adult (Kevin D. Arvin,

    locust borer larva

    Locust borer larvae (Whitney Cranshaw, Colorado State University,

    locust borer damage

    Locust borer damage (Whitney Cranshaw, Colorado State University,

    Pest Description

    • adults: 3/4 inch; black beetles with brilliant yellow markings
    • larvae: up to 1 inch long; white grubs without legs

    Host Plants, Diet & Damage

    • black locust and its cultivars (e.g., purple robe locust)
    • feed on the xylem of host trees
    • extensive tunneling in the wood may cause structural weakness of branches or trunk

    Biology, Life Cycle & Damaging Life Stage

    • overwinter as larvae in the bark
    • tunnel into and feed on heartwood in the spring and summer
    • adults emerge around August, mate and lay eggs on the bark
    • one generation per year
    • larvae are the damaging stage

    IPM Recommendations

    • Manage trees to improve or maintain overall health.
    • Prune infested wood/branches and chip or burn.
    • Apply an insecticide (carbamate; pyrethroid) to the bark on the trunk and large scaffold branches in late-July/early-August prior to egg laying.

    For more information, see our Locust Borer fact sheet.