Shothole Borer

    Shothole Borer

    Scolytus rugulosus 

    shothole borer

    Shothole borer (Pest and Diseases Image Library, Bugwood.org)

    shothole borer exit holes

    Exit holes produced by shothole borers (Clemson University, USDA Cooperative Extension, Bugwood.org)

    shothole borer galleries

    Shothole borer galleries produced by larval feeding (Shawn Steffan, Utah State University Extension)

    Pest Description

    • adults: 1/16 – 1/10 inch; black to reddish brown
    • have a “thumbnail-like” rear end
    • larvae: white grubs with a brown head capsule; no legs

    Host Plants, Diet & Damage

    • crabapple and other fruit trees; cydonia; hawthorn; elm
    • feed on phloem and sapwood
    • produce frass and oozing from holes in trees
    • attack cut, broken or unthrifty limbs or stems
    • when beetles emerge, they leave small “shotgun” holes in the bark
    • can introduce fungal pathogens

    Biology, Life Cycle & Damaging Life Stage

    • overwinter as larvae in sapwood chambers
    • one to two generations per year
    • emerge in April to mid-May
    • larvae are the damaging life stage

    IPM Recommendations

    • Reduce stress and keep trees healthy and damage free.
    • Prune affected material and remove from site, or debark.
    • Monitor fruit trees for signs of attack.
    • If known populations are nearby, an insecticide (carbamate; pyrethroid) applied to the bark prior to beetle flight can protect trees.

    For more information, see our Bark Beetles fact sheet.