Lumpy swellings along the stems of citrus trees are an indication of Citrus Gall Wasp. Citrus Gall Wasp (Bruchophagus fellis) is native to warm coastal areas in New South Wales and Queensland but has also become an increasing problem in Victoria and Western Australia. Its original host was the native Australian Finger Lime but can also seriously affect other citrus including Lemons, Grapefruit and Oranges.
There are 3 main stages in the Citrus Gall Wasp life cycle: 1. The small black adult wasp lays eggs underneath the bark on soft new spring growth. 2. Larvae hatch from the eggs, eat the stem tissue and the lumpy galls form around the developing larvae. 3. The larvae mature into the adult wasp which emerges from the gall the following spring, leaving small pin-prick holes.
The galls not only look unattractive, but they can also lead to poor plant health and a reduced harvest. It’s important to be vigilant and look out for these galls and winter is an ideal time to act to reduce this nasty pest, before the adult wasps emerge in spring.