What is a Rose Gall Wasp?
A rose gall wasp is a parasitoid wasp (tiny and harmless to humans) that lays its eggs in rose plant tissue. The wasp doesn’t sting people — it uses its ovipositor (egg-laying organ) to insert eggs into rose buds or new plant growth.
What Does a Rose Gall Wasp Do?
The wasp injects eggs and special chemicals or hormones into the plant. These chemicals trick the rose into forming a gall — a weird-looking, rounded growth that houses and feeds the developing larvae. The most famous gall caused by these wasps is the Robin’s pincushion, which looks like a fuzzy red or green ball.
Where Do You Find Rose Gall Wasps?
Rose gall wasps are found throughout Europe, parts of Asia, and North America. They live on or near wild roses, such as Rosa canina (dog rose) or Rosa rugosa. They prefer hedgerows, woodlands, and sunny open fields where wild roses grow.
I had never seen a rose gall or heard about a rose gall wasp until we purchased this current property that has a large, wonderfully scented wild rose that grows along the back property line. It is smothered in galls and I asked my sister (who has a degree in horticulture) what these funny looking little fuzzy balls were all over the canes — and that was my introduction to the little rose gall wasp.
Rose galls all over a wild rose
What Does a Rose Gall Wasp Eat?
Adults: Usually don’t feed much or at all; their purpose is to reproduce. Talk about a weird bit of trivia!
Larvae (inside the gall): Feed on nutritious plant tissue in the gall walls.
The gall acts like a customized pantry built by the plant, but manipulated by the wasp.
The Life-cycle of a Rose Gall Wasp
Spring–Early Summer: Adult female wasps emerge from old galls.
Egg-Laying: They lay eggs in new rose buds or leaves, injecting chemicals.
Gall Formation: The plant tissue swells and forms a protective gall.
Larval Stage: Larvae hatch and feed inside the gall for several months.
Overwintering: Larvae remain inside the gall through the winter.
Pupation: In early spring, they pupate (transform into adults) inside the gall.
Emergence: New adult wasps chew their way out and the cycle restarts.
Note the holes where the larvae were and the adults emerged from.
Are Rose Gall Wasps Bad for My Roses?
In most cases, rose gall wasps don’t seriously harm the rose plant. The galls they form (like the fluffy “Robin’s pincushion”) may look weird or unsightly, but:
They don’t spread through the whole plant.
They rarely kill branches or affect overall rose health.
They’re more of a cosmetic issue than a real threat.
What Should I Do with Rose Galls?
Option A: Nothing. Since this, in all likelihood, will not kills any of your roses, you can just leave it alone.
Option B: If you feel the galls are unsightly or getting out of control, you can prune off and destroy galls (especially before late fall) to interrupt the life cycle of the rose gall wasp.
