Strategies to control purple spot of asparagus (VX01024)

This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

Purple spot was a serious foliar disease of asparagus worldwide. In Australia, purple spot occured in every growing region, prematurely defoliating crops thereby reducing the carbohydrate storage potential and yield of the asparagus crown. This project had sought to investigate management strategies for purple spot in southern Victoria, from seed health to the mature crop. Control of foliar diseases would contribute to the longevity of the asparagus crown and assist in achieving sustainable yields. Strategies had been developed which resulted in heightened grower awareness of the disease and tangible outcomes that could be easily implemented on farm without compromising export and local market access. The following industry priorities have been addressed:

1. Management protocols to control purple spot disease at fern stage. Protocols were developed based on reviews of international literature and on farm field testing. Outcomes were delivered to growers as a factsheet set including:
   1. Disease identification, symptoms and conditions favouring disease.
   2. Determination of a purple spot disease threshold (when to spray).
   3. Disease risk analysis.
   4. Cultural and chemical control strategies: methods and timing of fungicide applications and removal of volunteer seedlings.
   5. Minor use permit applications for fungicides to control foliar diseases that would not compromise export or domestic market access ie no detectable chemical residues.
   6. Promotes scouting as a first line of defence tool against disease.
2. Seed hygiene protocol.
   1. Disinfestation of asparagus seed factsheet.
3. Nursery crown hygiene protocol.
   1. Monitoring for disease in nursery crowns.
   2. Keeping nursery crowns free of disease factsheet.
4. Tools to assist with the identification of major asparagus problems delivered to growers as a pocket guide “Pests, Diseases, Weeds and Disorders of Asparagus in Southern Victoria”.
5. Identification of the species of Stemphylium causing purple spot in Australia using DNA sequencing.
6. Note: An additional fungicide trial was conducted to control asparagus rust. This disease was first detected in May 2003 in Victoria. This trial was funded by Plant Standards, Victoria and was included in this report.

Recommendations included in this report provided asparagus growers with tools to manage a serious foliar disease and hygiene practices to minimise the impact of other diseases, especially exotic diseases, which threatened the viability of the Victorian asparagus industry. Future research was still a priority to keep abreast of pest and disease threats.