Managing soilborne diseases of onions (VN13003)
Status: Completed project
What was is it all about? This project had a focus on improving the management of onion stunt, a problematic soilborne disease that reduces the size and quality of onion bulbs and is caused by fungus Rhizoctonia solani AG8. The effects of root-lesion nematode Pratylenchus neglectus and pink-root-causing Setophoma terrrestris were also investigated. The research has culminated in the production of the Best practice guide for onion stunt, which will soon be made available on Hort Innovation’s onion grower page and in other industry channels.
Project activities included field work in 43 paddocks in South Australia over two growing seasons. A key part of the work was the evaluation of sampling strategies for the pathogens, to ultimately enable growers to determine the risk of onion stunt before planting (with most decisions to reduce the impact of soilborne diseases needing to be made and implemented before crop planting).
The researchers note that measuring Rhizoctonia solani AG8 DNA levels in the soil prior to planting provided a useful indication of the risk of onion stunt, with sampling prior to or early in the preparation of ground for sowing providing the best estimate of disease risk. The established protocol involves collecting four separate soil samples from along four transects around an onion pivot, and testing them individually to assess disease risk.
Prediction of disease risk was improved by also including the pre-planting numbers of Pratylenchus neglectus, which was associated with large areas of reduced plant growth and loss of yield in paddocks in the absence of Rhizoctonia solani AG8. Setophoma terrestris, was also associated with low productivity, especially in paddocks of red onions.
The knowledge developed lays the foundations for the delivery of a testing service to enable onion growers to identify the risk of onion stunt before planting, so they can implement appropriate management strategies to reduce losses.
The researchers also investigated cost-effective management strategies for onion stunt. Trials were conducted to assess the impacts of rotation crops, nurse crops and other pre-plant practices. For example, at sites where a high risk of onion stunt existed, the effectiveness of breaking up the Rhizoctonia solani AG8 fungal network in the soil by intensive cultivation and deep ripping to reduce disease risk was confirmed.
The importance of the choice of cereal nurse crop, and the timing of nurse crop removal, was also demonstrated in relation to competition with the onion seedlings and the build-up of Rhizoctonia solani AG8 at this critical growth stage.
As well as the best practice guide, full details of the research can be found in the project’s final report, which will soon be available to order at www.horticulture.com.au/about/resources-publications-final-reports. Final reports are free to Australian horticulture levy payers, registered Hort Innovation members and industry representative bodies.
Development of an onion white rot forecast model for Tasmania (VN14001)
Status: Ongoing project
What’s it all about? Onion white rot is a serious fungal disease. Beginning in 2016, this project will develop a forecasting model for its infection periods in Tasmania. It will identify conditions that precede high-risk infection periods, and help in understanding optimum timings of fungicide applications for control of the disease.
What’s the latest update? During the 2015/16 season, pilot studies were conducted to test and develop the research methodologies in the project. It will be data collected from commercial field crops and in-situ planter bag trials during the 2016/17 and 2017/18 seasons that will be used to develop the disease model itself.
Six commercial field trails sites have now been established in north-west and northern Tasmania, with monitoring commenced. Planter bag trials have also been established at the Tasmanian Institute of Agriculture Vegetable Research Facility in north-west Tasmania.
The planter bag trials will measure root growth, timing of infection and effect of inoculum soil, while root growth will be assessed in commercial crops, and the development stage of crops will be monitored for all trials. Environmental data will also be collected at all project sites, including soil temperature, soil moisture, air temperature and humidity.
From the data there will be three versions of the forecast model created, to account for three key onion planting periods: May, July and September. The data will be presented as a fact sheet detailing for each planting window the combinations of soil temperature, soil moisture and crop growth stage that signal the start of infection periods.
Classification of the onion rust complex and development of rapid diagnostic assays (VN13001)
Status: Completed project
What was it all about? With onion rust identified as a key biosecurity risk to the industry, this project sought to determine which rusts infect the onion family in Australia and overseas, and to develop reliable diagnostic markers and tools to identify them.
The project’s final report is soon to be submitted to Hort Innovation, and will be ultimately be available to order at www.horticulture.com.au/about/resources-publications-final-reports. Final reports are free to Australian horticulture levy payers, registered Hort Innovation members and industry representative bodies.
The project’s findings will also be incorporated into a lab diagnostic manual, to be submitted to the Subcommittee on Plant Health Diagnostic Standards.
Australian onion industry communications (VN15002)
Status: Ongoing project
What’s it all about? This project delivers effective and timely communications to ensure Australian onion growers and other industry stakeholders are kept up-to-date with the latest R&D outcomes, marketing activities, and other industry news and information. In communicating R&D in particular, the ultimate goal is to lead to practice change for growers, boosting productivity and profitability.
The project is also supported by Communication support on VN15002 – Australian onion industry (VN15003).
What’s the latest update? A number of regular communication channels continue to be produced and maintained by this project, including but not limited to:
- The Onions Australia website, www.onionsaustralia.org.au, which was updated and relaunched at the start of February this year
- The Onions Australia annual magazine, available to download here
- Monthly e-newsletters from Onions Australia, available to download here
- Layers newsletters, distributed three times annually
- Twice-yearly OnionSTAT reports
- Social media, via the Onions Australia Facebook and Twitter accounts
- Other resources as needed.
The new-look Onions Australia website, relaunched as part of project VN15002
Detection and management of bacterial diseases in Australian allium crops (VN13005)
Status: Ongoing project
What’s it all about? Due for completion this year, this three-year project has been investigating bacterial diseases of onion crops in order to build the industry’s capacity to manage them, and to enhance the industry’s preparedness for potential incursions of exotic diseases.
What’s the latest update? No new milestone report was due in the period since the last edition of Hortlink (Spring 2016). At the time of last reporting, investigation of potential bacterial disease-control measures had commenced.
- The researchers noted there are currently no products registered by the Australian Pesticides and Veterinary Medicines Authority specifically for the control of bacteria in onion crops. There are, however, over 40 copper-containing products registered for other uses in onions, and potential to expand the registered use of some of these products for the control of bacterial diseases.
- In regards to Pseudomonas syringae porri (Psp), which causes bacterial leaf spot, there are a range of non-copper products that may be effective control measures. The project was to begin investigating a range of essential oils to this end.
- Fourteen commercial onion varieties were to be screened for resistance or tolerance to Psp.
Other R&D projects of note…
- Review of the National Biosecurity Plan for the onion industry and development of a biosecurity manual for onion producers (VN15001), which was contracted for the industry in October. With project activities recently underway, a more detailed update will be provided in the next edition of Hortlink.