European Elm Scale

    European Elm Scale

    Gossyparia spuria

    european elm scales

    European elm scales (Joseph Berger, Bugwood.org)

    european elm scales

    European elm scale crawlers/nymphs (Whitney Cranshaw, Colorado State University, Bugwood.org)

    european elm scales

    European elm scale male cocoons (Whitney Cranshaw, Colorado State University, Bugwood.org)

    Pest Description

    • females: ~ 5/16 inch; oval; brown with a white fringe
    • males: smaller than females; male cocoons appear as white, puffed rice
    • immatures: crawlers (mobile stage) ~ 3/64 inch, yellow orange; wingless
    • immatures: nymphs flattened and oval; translucent yellowish
    • overwintering immatures with a light gray-white waxy coating

    Host Plants, Diet & Damage

    • elm; common on ‘Camperdown’ elm in Utah
    • feed on plant sap from twigs, small branches and leaves
    • leaf yellowing and premature leaf drop
    • severe infestations may kill branches
    • honeydew production leads to sooty mold on leaves and branches

    Biology, Life Cycle & Damaging Life Stage

    • overwinter as 2nd instar nymphs in bark cracks or twig notches
    • ]reach maturity and mate from mid-April to late-May
    • egg hatch occurs from mid-June to mid-July
    • crawlers settle on the undersides of leaves along main veins
    • one generation per year
    • nymphs and adults are the damaging stages

    IPM Recommendations

    • Manage trees to improve or maintain health.
    • Monitor scale populations on host plants.
    • Apply an insecticide (carbamate; horticultural oil; insecticidal soap; organophosphate; pyrethroid) to coincide with scale crawler activity.
    • Apply a systemic neonicitinoid in spring after leaves have expanded.

    For more information, see our Soft Scales in Utah Landscapes fact sheet.