Eucalyptus gall wasp

What is eucalyptus gall wasp?

The gall wasp is a minute black insect whose larvae develop inside raised galls that form on eucalyptus leaves during spring.

Symptoms

• Slightly raised swellings, about 1mm in diameter, develop on either side of eucalyptus leaves
• These pinkish-brown galls can be mistaken for a physiological disorder known as oedema, but the galls are hollow and each contains a tiny white grub. The galls are also of uniform sizeand shape 
• Oedema growths are solid and more irregular in size and shape. The galls are most noticeable in early spring when infestations can cause heavy leaf fall

Control

Non-chemical control

• Collect and dispose of fallen leaves in spring as this will prevent some of the gall wasps completing their development

Chemical control

• On tall trees, control is not possible
• If the tree is small enough for the foliage to be sprayed thoroughly, a systemic insecticide such as thiacloprid (Bayer Provado Ultimate Bug Killer) or acetamiprid (Scotts Bug Clear Ultra) applied in late May may give some protection

Download

Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

Biology

• The black adult wasps are 1mm long and they emerge in late May to June
• The identity of this gall wasp is currently uncertain but they are close to an Australian species, Ophelimus maskelli
• Females lay eggs on new eucalyptus foliage in early summer, and the larvae develop within the leaves, although the raised galls do not become particularly obvious until the following spring, when the mature larvae pupate within the galls