Oak Apple Gall Wasp

Biorhiza pallida

Oak Apple Gall Wasp, Oak Gall Wasp

Andricus fg16 by Fritz Geller-Grimm (CC BY-SA 3.0)
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A close up of a Biorhiza pallida apple oak gall wasp on a leaf
Andricus fg16 by Fritz Geller-Grimm (CC BY-SA 3.0)
1 of 4
Oak Gall Wasps are tiny gall-forming insects that look very similar to flying ants. These insects belong to a specialised group of insects called parasitoid wasps. They require a plant host to survive and reproduce. Gall Wasp eggs are laid in the shoot tips of new leaves. The plants begin to rapidly-produce cells, and growth becomes malformed. Plants produce tumour-like structures, which resemble something similar to an apple. These home the gall wasp larvae. The large, spherical galls can be seen in Oak from as early as spring.
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Traits

Cause plants to produce apple-like growths that can be unsightly.
Galls won't permanently damage the host plant.

Appearance

Adults: These wasps are tiny and elusive so it's unlikely you'd see them. The gall wasp eggs and larvae remain inside the plant and gall. Identification can best be achieved from the plant galls that arise on the plant. Galls: These wasps produce galls in oak which look similar to apples. They can be as large as 4 cm and when touched may feel spongey. They begin white and pink, but eventually, turn brown once the contents of the gall have been depleted by the wasp larvae inside.

Symptoms

Large, spherical structures may become evident near areas of new growth, on twigs and beneath leaves.

Activity

Diurnal

Personality

Order

Hymenoptera

Family

Cynipidae

Metamorphosis

Complete

Distribution

Europe

Biological treatment

This wasp will not impact the longterm yield of trees, but the galls it produces may be unsightly. Gall wasps seem to be more frequent in some years than others, so trees typically have quieter periods to recover.

Chemical treatment

Insecticides are unlikely to work on this wasp.

Attracts

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