May Pest of the Month: Galling insects

The most common gall inducing insect groups in Australia include aphids, midge flies and gall wasps. There are a variety of other groups that also sometimes produce galls, in particular thrips, psyllids and scale insects.

Gall-inducing insects tend to be specialist plant feeders, only feeding on one, or a small number of closely related host plant species. The interaction between the host plant and gall-inducing insect is very complex. Each species produces a very specific type of gall, which can sometimes be used to identify the causal insect. However, sometimes more than one species can produce galls of similar appearance on the same plant.

Damage can be varied and include lumps, blisters, leaf and stem deformation. A small amount of damage can sometimes cause plants to be unsaleable. The presence of damage is seen long after the initial infestation and is often the only method to detect that the pest is in the crop. By the time damage is seen, the crop can be unsaleable.

Therefore, it is important to put in place proactive management strategies for any gall insects that are regular damaging plants at your business. The exact management actions used will depend on the pest species and host plant.

The gall insect pest management plan has information on the management of the major gall pest groups and includes cultural actions and pesticide recommendations.

Figure caption: Gall midge fly larvae under the leaf sheath of Dianella.