Wasps bite back

A NATIONAL project under the lead of NSW Department of Primary Industries (DPI) entomologist, Jianhua Mo, aims to manage the devastating citrus gall wasp (CGW) by targeting the pest with its natural enemies, new generation pesticides and environmentally-friendly repellents.

Based at the Yanco Agricultural Institute, Dr Mo said CGW has recently emerged as a major pest in southern citrus crops, infesting orchards in the Sunraysia, Riverland and Riverina to impact on plant vigour, fruit size and citrus yields.

“We’re building on results from a pilot study in the Sunraysia, which developed a timing guide to target vulnerable stages of the pest, identified an alternative chemical treatment using paraffinic oil and confirmed the establishment of two native parasitic wasps which attack CGW,” Dr Mo said.

“Studies in Queensland, where CGW and their natural enemies originated, showed that when parasitic wasp populations are high, up to 90 per cent of gall wasp larvae can be parasitised.

“The new project aims to develop national integrated pest management (IPM) strategies based on enhanced biological control, repellent sprays, new chemical options compatible with IPM and a robust forecasting tool to guide spray timing and releases of parasitic wasps.

“Two native parasitic wasps, Megastigmus brevivalvus and M. trisulcus, are valuable natural resources in our quest to manage the pest.

“With both species now established, we are identifying parasitic wasp hotspots to conserve their populations in southern citrus regions and releasing parasitic wasps in new CGW incursion areas to boost their effects in managing the pest.”

Dr Mo said studies are currently under way to develop best management practices for wasp releases and improved spray control and repellent options.

“It’s important to manage the pest in an environmentally-friendly way that allows growers to produce healthy citrus crops and meet consumer demand.”

Funded by DPI and Horticulture Innovation Australia (Hort Innovation), the CGW management project brings South Australia’s Fruit Doctors and Department of Agriculture and Food Western Australia on board as research partners.

Hort Innovation chief executive officer, John Lloyd, said the project which is due to run until 2018, has far reaching benefits.

“Using grower levies, the national program is working with citrus growers to raise awareness of CGW biology, damage and management and deliver the tools industry needs to better manage the pest,” Mr Lloyd said.