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Eucalyptus Gall Wasp

Ophelimus spp.

Eucalyptus Gall Wasp

Ophelimus maskelli galls on Eucalyptus

by Giancarlo Dessì. CC BY-SA 3.0

A close up of a tree leaf infested with Ophelimus Eucalyptus gall wasp
Eucalyptus Gall Wasps are tiny fly-like wasps. They're parasitic wasps, which means they require a living host to reproduce successfully. Ophelimus spp. are solitary; unlike yellowjacket wasps who live in social nests with multiple individuals. They use the leaves of Eucalyptus to lay their eggs. Eucalyptus plants respond to infestations by producing abnormal bumps, called galls. The wasp's larvae develop inside the gall until mature, emerging as adult wasps. Ophelimus spp. is most damaging in Eucalyptus plantations, and less so in gardens. Usually, the first symptom noticed is infested leaves falling prematurely. The Eucalyptus Gall Wasp has not long been in the UK. The rash-like galls left by larvae are the best way to detect them on Eucalyptus.
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Traits

Cause brown galls, or raised bumps, to develop on Eucalyptus.

Appearance

Adults: The wasps are so small it's unlikely you'd see them. They are completely black and are smaller than 1mm, they can easily be mistaken for small flies. Galls: Identify parasitic wasps using the galls. Look out for raised swellings on both sides of Eucalyptus leaves. These swellings are around 1mm wide and pink-brown or sometimes they're yellowish-green. There will be a tiny grub in each gall.

Symptoms

Red-brown or greenish-yellow bumps on Eucalyptus leaves. Infested leaves fall prematurely.

Activity

Diurnal

Personality

Order

Hymenoptera

Family

Eulophidae

Metamorphosis

Complete

Distribution

Parts of Europe, Asia and Africa, Australia

Biological treatment

This wasp will not impact the longterm vigour of trees, but the galls it produces may be unsightly. To avoid reinfestation, pick up and destroy infected leaves which have fallen to the ground and this may help control numbers the following year.

Attracts

Some peeling Eucalyptus bark

Gum

Eucalyptus spp.

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