Rose Gall Wasps

    Rose Gall Wasps

    Diplolepis spp. 

    rose gall wasp

    Rose gall wasp (Thiotrix, Wikimedia Commons)

    mossyrose wasp galls

    Gall made by mossyrose gall wasps (Milan Zubrik, Forest Research Institute - Slovakia,  Bugwood.org)

    rose galls

    Galls made by rose gall wasps (Oliveoligarchy, Wikimedia Commons)

    Pest Description

    • adults: very tiny and seldom seen
    • larvae: grub-like; found within galls
    • pest noticed by the presence of galls
    • each species creates a unique gall

    Host Plants, Diet & Damage

    • most common on roses and oaks
    • galls can occur on acorns, branches, buds, flowers, leaves, roots and twigs
    • larval feeding causes round, spiny, single/multiple or other types of galls
    • galls do not typically affect the overall health of the tree
    • excessive galling of branches and twigs can cause plant stunting or dieback

    Biology, Life Cycle & Damaging Life Stage

    • overwinter as larvae in the gall
    • pupate within the gall or in the soil in spring
    • emerge in April and May, coincident with budbreak
    • eggs laid on emerging plant tissue or on/in swollen buds
    • larval feeding produces galls
    • most have one generation per year
    • larvae are the damaging stage

    IPM Recommendations

    • Galls do not affect the overall health of the tree; tolerate pest.
    • Rake and remove fallen leaves in the fall.
    • Remove galled plant parts and destroy.
    • Management with insecticides can be difficult and spotty.
    • Apply an insecticide (carbamate; pyrethroid) at or just prior to budbreak to prevent egg laying to reduce gall formation (may not prevent all new gall formation).