Oak Gall Wasp

Neuroterus spp.

Oak Gall Wasp, Gall Wasp

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A close up of galls produced by gall wasps in the Neuroterus genera
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Oak Gall Wasps are tiny-black gall-forming insects that belong to a highly specialised group of wasps. Sometimes they're called parasitoids or parasitic wasps. Parasitic wasps need a host to survive; however, the damage they cause is never detrimental to the host, in most cases. Plant galls can be more numerous some years more than others. A gall looks like an abnormal growth, and the wasps belonging to the Neuroterus genus will produce galls that look similar to buttons or disks that grow beneath the plant leaf. A larva feeds inside the button gall. When large enough, the larva wriggles until the gall falls to the ground, which is where they undergo the final stage of development.

Traits

The presence of these insects cause host plants to produce abnormal growths or tumours, known as plant galls.
Gall wasps won't do permanent damage to plants.

Appearance

Adults: Adult wasps are so tiny it's unlikely you'd see them. Adult wasps are more similar to ants because of their size and colour. Galls: The galls are incredibly diverse and differ significantly between wasps. Most of the time, it can be relatively easy to find out what kind of insect has caused them to arise. Neuroterus gall wasps produce 'button' or 'spangle' galls that look a bit like small flattened disks. These are typically attached to the underside of oak leaves and can be green, red, yellow, orange or brown. The gall wasp eggs and larvae remain inside the plant and gall.

Symptoms

Small, button-like structures under the leaves of oak. Galling-behaviour can sometimes reduce yields.

Activity

Diurnal

Personality

Order

Hymenoptera

Family

Cynipidae

Metamorphosis

Complete

Distribution

Worldwide

Biological treatment

This wasp won't impact the longterm yield of trees, but the galls it produces may be unsightly. Gall wasps seem to be more frequent in some years compared with others. Trees typically have quieter periods in which they recover. You can pick leaves from trees and dispose of them accordingly.

Chemical treatment

Insecticides are unlikely to work on these wasps. It's suggested to pick up and destroy any leaves that have been infested and fallen to the ground. This may help control numbers the following year.

Attracts

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