Elm Seed Bug

    Elm Seed Bug

    Arocatus melanocephalus

    elm seed bug

    Elm seed bugs (Ryan Davis, Utah State University Extension)

    elm seed bug

    Late instar nymph (Ryan Davis, Utah State University Extension)

    elm seed bug feces

    Elm seed bug feces (Ryan Davis, Utah State University Extension)

    Pest Description

    • adults: 1/3 inch; alternating black and red pattern outside of wings; red underside (abdomen)
    • triangular segment behind head is black and surrounded by red on the top portion of the wings
    • nymphs: smaller; red abdomens and black wing pads and head

    Host Plants, Diet & Damage

    • elm; linden
    • feed primarily on sap from elm seeds and leaves
    • no damage done to tree
    • congregate on structures and can come indoors during hot periods of the summer
    • overwinter in cracks, crevices, leaf litter and in buildings
    • may stain lightly colored materials with fecal material
    • emit an unpleasant odor when bothered

    Biology, Life Cycle & Damaging Life Stage

    • overwinter as adults in and around homes
    • become active in March with warming temperatures
    • adults lay eggs on elm seeds and trees in May
    • one generation per year, but overlapping life stages may be present

    IPM Recommendations

    • No damage to trees; nuisance pest only.
    • Remove unwanted/volunteer elm trees in the area if possible.
    • Seal cracks that may allow bugs to enter buildings.
    • Vacuum to remove indoor and outdoor populations.
    • Remove elm seeds that have collected around buildings.

    For more information, see our Elm Seed Bug fact sheet.