A three-year, $1.2 million research project into Cucumber Green Mottle Mosaic Virus (CGMMV) has made a number of recommendations to better understand and manage the disease.

CGMMV is a plant disease that infects fruit and vegetables belonging to the family Cucurbitaceae, which includes watermelon, cucumber, melons, zucchini, pumpkin, squash, and Asian cucurbit vegetables such as bitter gourds and bottle gourds.

It was detected in watermelon farms in the Northern Territory in September 2014. Since the initial detection, CGMMV is now also found in isolated areas of Queensland, South Australia and Western Australia.

Department of Primary Industry and Resources Principal Plant Biosecurity Officer Dr Lucy Tran-Nguyen led the CGMMV research project.

“The department was provided with $1.2 million from Hort Innovation in 2016 to undertake this research into CGMMV,” Dr Tran-Nguyen said.

“It has been nationally agreed that it is not feasible to eradicate CGMMV from Australia and a national management plan has been developed to contain the plant disease to known infected areas, prevent its spread, and minimise disruption to domestic and international trade.

“A critical part of CGMMV management is identifying possible sources of the disease that could result in reinfection, so the research project focused on determining the spread and impact of the disease.

“It focused on the importance of weeds, non-host plants and honeybees on the distribution and control of CGMMV, and examined how current in-field diagnostics can help quickly detect the virus on farms that are known or suspected to be infected with CGMMV.

“We investigated six crops to determine whether they were CGMMV hosts, and found that sweet corn, snake bean, capsicum, okra, sorghum and peanut were all non-hosts, meaning using these crops as cover crops can help manage CGMMV.

“A number of weeds were found to host CGMMV and could be potential pathways for CGMMV spread, so it was determined that weed management is important in managing the plant disease.”

Previous trials had shown CGMMV can remain in soil for at least 12 months, even without a host plant present, so the research project looked at the susceptibility of new plantings in soil where infected plants had previously been grown.

“We experimented with clean seeds and seedlings and found that directly sowing seeds in contaminated soil produced less infected plants compared to the transplanted seedlings due to the damaged root systems allowing the virus to enter the transplants,” Dr Tran-Nguyen said.

“Our research also found that while CGMMV can be present in bees, brood, pollen, propolis, wax and honey, live CGMMV was only found in adult bees, pollen and honey

“While more work still needs to be done to determine the transmission pathways between bees and plants, it is good practice to know where your bees have previously worked.”

The research team developed a suite of communication and extension materials to help cucurbit growers, and has presented research findings throughout the project at field days, scientific and industry conferences, and growers meetings across the Northern Territory and Australia.

The project has been funded by Hort Innovation, using the vegetable industry research and development levy and contributions from the Australian Government. Hort Innovation is the grower owned, not-for-profit research and development corporation for Australian horticulture.

The NT DPIR research was supported by the Northern Territory Farmers Association, Queensland Department of Agriculture and Fisheries, Victorian Department of Jobs, Precincts and Regions, and the New South Wales Department of Primary Industries.

The research fact sheets developed as part of the project are available on the Department of Primary Industry and Resources website: www.dpir.nt.gov.au.