Bronze Birch Borer

    Bronze Birch Borer

    Agrilus anxius

    bronze birch borer

    Bronze birch borer (Whitney Cranshaw, Colorado State University, Bugwood.org)

    bronze birch borer larva

    Bronze birch borer larva and gallery (David G. Nielsen, The Ohio State University, Bugwood.org)

    bronze birch borer damage

    Bronze birch borer damage to birch tree (Steven Katovich, USDA Forest Service, Bugwood.org)

    Pest Description

    • adults: 1/4 – 3/4 inch; slender; bronze black
    • larvae: creamy white with an enlarged head area; tapeworm-like appearance

    Host Plants, Diet & Damage

    • birch, especially paper birch
    • feed on phloem and etch sapwood of trunk and branches
    • create serpentine galleries under the bark
    • galleries may be externally visible on trunk as raised bumps
    • leave diagnostic, D-shaped exit holes in bark
    • can cause canopy dieback or complete tree death

    Biology, Life Cycle & Damaging Life Stage

    • overwinter as larvae under the bark or in the sapwood
    • adults present late-May through August (peak in July)
    • eggs laid singly or in groups under bark flaps
    • early in an infestation, attacks are focused on smaller branches in the upper canopy
    • one generation per year is typical, but may take 2 years
    • prefer stressed, weakened trees
    • *bronze poplar borer (Agrilus liragus) is a similar species on Populus spp.
    • larvae are the damaging stage

    IPM Recommendations

    • Avoid planting susceptible birch species, especially paper, silver and gray birch.
    • Monarch birch, Japanese white birch and river birch are more resistant.
    • Keep trees well watered.
    • Minimize iron chlorosis to reduce stress.
    • Apply an insecticide (pyrethroid; carbamate) to stem and branches.
    • Apply a systemic neonicitinoid soil drench (imidacloprid) or granular (dinotefuran) after leaf expansion.