San Jose Scale
San Jose Scale
The eucalyptus gall wasp is a tiny fly-like wasp. These wasps belong to a diverse family containing parasitoid wasps, which means they need a living host in order to survive. They are extremely hard to identify, and specimens deteriorate rapidly due to their size, so even some museum specimens still lack identification. The Eucalyptus gall wasp has not long been in the UK. The rash-like galls left by larvae are the best way to identify this species presence.
This insect causes multiple pink-brown galls, or raised bumps, to develop on both sides of infested Eucalyptus leaves. It's often confused with oedema, a physiological disorder in plants.
These wasps are so small it's unlikely you'd see them. However, they are completely black and are smaller than 1mm. Their presence is best detected from the galls produced by the wasp larvae. Look out for raised swellings on both sides of the leaf. These swellings are around 1mm wide and pink-brown. There will be a tiny grub in each gall. Galling behaviour can cause the leaves to drop from trees- and in most cases, it's at this point infestations are noticed by gardeners.
Leaves covered in raised bumps, or swellings, that are pinky brown. Leaves falling from trees prematurely.
Parts of Europe, Asia and Africa. Widespread across Australia.
This wasp will not impact the longterm vigour of trees, but the galls it produces may be unsightly.
Insecticides are unlikely to work on this wasp. It's suggested to pick up and destroy any infected leaves which have fallen to the ground and this may help control numbers the following year.