Area wide management of vegetable diseases: viruses and bacteria (VG16086)

What was it all about?

From 2018 to 2023, this program aimed at developing area wide management (AWM) strategies to address high-priority viral and bacterial diseases affecting vegetable crops. These diseases impact producers nationally, collectively costing millions of dollars each year.

A wide range of activities occurred over the duration of the program.  All activities were led by the Department of Agriculture and Fisheries Queensland as well as the NSW Department of Primary Industries, who delivered separate parts of the program.

For the Department of Agriculture and Fisheries Queensland portion of the project…

National annual disease surveys were undertaken to capture current disease pressures, review past disease research and new research through multiple management trials and genetic diversity studies of pathogens and vectors.

Trials were conducted in multiple districts for known highly impacting diseases (e.g mosaic of zucchini and viruses of capsicums) and for pectobacterium affecting zucchini which was identified through early surveys as an emerging concern. These activities also generated a priority list of endemic and exotic diseases of concern for the Australian vegetable industry.

Additionally, the project delivered a second important outcome through improved biosecurity preparedness to six key exotic threats for the Australian vegetable industry. Contingency plans and factsheets were prepared for three exotic virus groups and three bacterial diseases.

Specific industry impacts and benefits from this project include:

• Improved resilience to manage viral and bacterial diseases (for both field and protected cropping systems)
• Increased capacity for disease management through a reconnected national network of experts in the fields of virus and bacteria diseases. This also included training four PhD students, two in plant virology and two in plant bacteriology and industry stakeholders through extension activities
• Improved diagnostic capability nationally which provides faster results for producers when seeking confirmation of causal agents for disease outbreaks. Twenty-three assays were circulated and validated through the national diagnostic services, including 16 for viruses and 7 for bacteria.
• Accurate and fast diagnostics assists with early disease management interventions
• Delivery of four hands-on pest and disease identification training workshops
• Improved understanding of the potential of seed as a pathway for endemic and exotic pathogens to affect Australian production. All stakeholders including growers, seed companies, biosecurity agencies, nurseries, AusVeg and Hort Innovation participated in two workshops on this topic.
• A disease priority list to inform on future R,D&E investment for crop protection.

Multiple resources were generated for the industry and available through the Hort Innovation website. These include:

• A guide to understanding and managing bacterial diseases affecting Australian vegetable crops
• A guide to understanding and managing virus diseases affecting Australian vegetable crops
• Nine specific factsheets on virus diseases affecting vegetable crops
• Six contingency plans
• Priority list of endemic and exotic pathogens.

For the NSW Department of Primary Industries portion of the project…

The key focus of this project was to minimise the effect of high impact endemic viral and bacterial diseases while taking a proactive approach to minimise the introduction and establishment of exotic vegetable diseases. The first step in this process was to develop an understanding the distribution and diversity of viral and bacterial pathogens endemic to NSW, addressed through three years of surveillance and working with farmers to identify the pathogens affecting their crops.

This involved visiting 64 growers, many with repeat visits, and diagnosing 869 samples. This work was complemented with genomic and field trial studies using the prevalent pathogens watermelon mosaic virus (WMV) and Xanthomonas campestris, responsible for black rot, to investigate the link between genetic diversity and pathogenicity and survivability of the pathogen in plant debris. 

The key output of this project is the baseline survey work that was conducted. In addition to undertaking a thorough disease census of the viral and bacterial diseases present in the NSW vegetable industry, the research team formed relationships with growers, provided training and cultivated the networks necessary for better management of current and potential future disease threats.

The surveys also uncovered a new virus, knowledge around establishment of viruses into NSW and weed hosts that pose transmission risks. Genomic studies showed that there are several WMV types present in NSW. Virus trials were conducted investigating breakdown of the virus with different composting methods and evaluating resistant crop varieties and alternative weed hosts. Xanthomonas campestris and Pseudomonas spp. are the dominant bacterial pathogens causing problems in the NSW vegetable industry. Genome studies of X. campestris identified several different clonal groups and isolates have been used in the development a new diagnostic assay and to investigate if genetic diversity translates into more pathogenic strains. The research team also investigated how long X. campestris survives in plant debris when buried or left on the surface, finding that X. campestris can survive for extended periods in infected plant debris and this poses a risk for on farm health of brassica crops. 

This project also supported capacity building for the vegetable industry in the form of training and development of vegetable pathologists working in our diagnostic service. The NSW DPI project personnel have also trained and participated in emergency biosecurity responses, some directly related to the vegetable industry, thus enhancing our capacity to respond rapidly and effectively in the event of a new exotic disease detection.

Overall, project outcomes have led to a better understanding of vegetable diseases and how to better identify and manage them. While this is just the tip of the iceberg, incorporation of this knowledge into farming practices in larger Area Wide Management plans can make all the difference.

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Access outputs from the project including:

• Guide to identification and management of major virus diseases affecting Australian field vegetable crops
• Guide to understanding and managing bacterial diseases affecting Australian vegetable crops.