Citrus gall wasp is a native species that has spread south and now west from its origins in coastal Queensland and northern New South Wales. Latest advice from the Department of Primary Industries and Regional Development in WA advises citrus tree owners to implement control measures to reduce the threat to the citrus industry in Western Australia and to continue to enjoy home-grown citrus fruit.
The department says the pest was probably introduced through infected citrus trees. It produces distinctive galls (swellings) on twigs and branches. See more of about the spread of the pest and its recommended control here. The pest does have natural predators, but these are slow to follow the fast-spreading pest.