Citrus Gall Wasp

Citrus gall wasp alert: new control project

Jianhua Mo, Steven Falivene & Andrew Creek, NSW DPI

October 2015

A gall that has been peeled back to show the wasps emerging.

Citrus gall wasp is an endemic citrus insect pest in Australia that is spreading throughout the southern citrus growing regions in NSW. It is expected to hatch out of galls from mid October through to mid November. It is best to target control options with systemic insecticides at egg hatch that occurs in December.

Spraying of adults wasps may not be effective because they emerge over a long period. Trials are underway to evaluate new insecticide options and other practical management solutions. One of soft control options being tested by the team is Kaolin clay applied just before gall wasp emerge (now) to act as an egg laying deterrent. For more information on control strategies contact your horticultural advisor.

Horticulture Innovation Australia has funded a project to investigate practical solutions to manage the citrus gall wasp. Dr Jianhua Mo, a Research Entomologist with NSW Department of Primary Industry (DPI) at Yanco, will lead the research. The project team includes staff from the South Australian organisation Fruit Doctors and NSW DPI to manage research trials in the Riverland, Sunraysia and Riverina districts.

Dr Mo and Steven Falivene inspecting a gall on some new growth that has been caused by a gall wasp.

Female citrus gall wasps lay eggs between the bark and wood of spring flush twigs (new growth). Upon hatching, the larvae burrow into the bark where they feed, develop and pupate. The larval feeding area of the twig swells, forming the characteristic galls. Heavily infested trees can be covered in galls and have reduced fruit size and yields.

Citrus gall wasp parasite — The citrus gall wasp parasite is very small but can help to reduce the severity of the infestation.

Research will initially focus on finding alternative chemical management
solutions for the pest. The longer term goals are to further develop parasitic wasp dispersion to target the gall wasp, and develop forecast models for citrus gall wasp emergence and egg hatching.

In 2014, NSW DPI updated a PrimeFact on the citrus gall wasp .

Email Jianhua Mo for further information about the project or phone 02 6951 2537.