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Oak Gall Wasp

Cynips spp.

Oak Gall Wasp, Gall Wasps, Cynipid Galls, Gallflies

A close up of an Oak gall wasp in the Cynips genus on a leaf stem
Cynips sp beentree by Beentree (CC BY-SA 4.0)
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Oak Gall Wasps are tiny insects that look very similar to flies or flying ants. Gall Wasps are highly specialised parasites which require plants to lay eggs successfully. They lay eggs within the foliage of plants, and this results in some form of abnormal growth known as a gall. There are many types of gall. They may be unsightly, but they never damage the plant or tree. Each gall is almost individual to the wasp causing it to occur. Cynips Gall wasps are well-known for their large spherical galls which form on the undersides of oak leaves.
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Gall wasps cause plants to produce abnormal fleshy growths called galls.
Galls aren't overly damaging and some years are worse than others.


Adults: These wasps are tiny and elusive so it's unlikely you'd see them. Their galls, on the other hand, are incredibly diverse and differ significantly between genera. Gall: The spherical galls characterise this genus of gall wasp. The galls appear as perfect spheres, protruding from the underside of the leaf. Some wasps will cause multiple galls to form on one leaf, whereas some will only result in a single gall. Galls can be pink, yellow, red, green and brown. Some will have smooth textures, but some can appear bumpy or spiky too.


Large, spherical structures may become evident underneath the leaves of oak.












Biological treatment

Although the galls may be unsightly, they won't impact the longterm yield of trees. Gall wasps seem to be more frequent in some years than others, so trees typically have periods to recover.

Chemical treatment

Insecticides are unlikely to work on this wasp.



Quercus spp.

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