Development of regional disease risk models for fungal diseases of pyrethrum (PY20000)
What’s it all about?
This project is investigating the environmental conditions that drive tan spot and ray blight outbreaks in pyrethrum. These diseases represent a major risk to yield and the industry’s ability to consistently meet market production requirements. Managing for disease is a major financial and environmental cost, and any effort to reduce those costs without major yield losses would be beneficial for pyrethrum growers.
A range of research activities are being undertaken and their results will be used to develop models that identify the relative risk associated with cropping regions and seasons. This information will be used to create a framework for industry decisions regarding frequency and timing of fungicide applications in pyrethrum.
This approach will ensure that high-risk regions are given adequate protection from disease losses but will also lead to an overall reduction in control costs for the industry by reducing fungicide sprays in low-risk regions and seasons.
The research for this project will fall into three areas:
- Climatic effects on disease. A series of controlled environment experiments will be conducted to examine the conditions that favour spore formation, spore germination, leaf infection and host colonisation.
- Regional differences in pyrethrum diseases. Regional differences will be monitored from autumn to early summer in both 2021 and 2022.
- Relationships between disease pressure and yield loss. Field data will be collected from field crops across three growing seasons.
The data obtained during the research activities will be combined to develop disease risk models for the impact of tan spot and ray blight on pyrethrum yield.
Collection of samples and data from field trials over two seasons and 20 survey sites from each of two seasons across northern Tasmania and Ballarat in Victoria has now been completed in this project. Final risk model development is now ongoing.
Based on interim data analyses, high cropping density within a district and high atmospheric moisture during late winter and spring appear key determinants of foliar disease outbreaks in spring. Spring appears to the key period at which pyrethrum is most vulnerable to foliar disease. Levels of both ray blight and tan spot in early October are highly correlated with crop yield losses at harvest. In late spring, foliar ray blight levels are correlated with yield losses, but not tan spot. By summer trial work has demonstrated that foliar and/or floral disease have little impact on crop yield. Thus, it is recommended that the timing of fungicide applications be concentrated over the spring growth period.s
2022 regional monitoring initiated
- Monitoring of the timing of foliar disease in commercial cropping during the 2022/23 growing season was initiated in 20 fields in North-West Tasmania and Ballarat during winter.
- Intensive monitoring is ongoing at six sites, spread across three distinct cropping regions across North-West Tasmania. Monitoring will continue until early summer.
2022 Disease impact trials initiated
- Two trial sites (54 plots each) incorporating spring fungicide applications have been set up in commercial fields and trial work is underway. Data on the pathogen load within individual plots will collected up until mid-October with yield data collected in January 2023.
- Three trial sites (36 plots each) were established in September 2022. These incorporate late spring and early summer fungicide applications. Pathogen load will be sampled for in October, November, and January, and combined with yield estimates collected in January.
Climate effect on spore germination studies completed
- Initially planned research studies into the impact of climate on spore germination were concluded in July 2022. However, data collected in this work suggests that additional in vitro studies are required to confirm the results obtained. These studies are planned for late 2022 and will not impact on the successful completion of PY20000.
From winter to early summer 2021, monitoring of the timing of foliar disease in commercial cropping was conducted at six sites spread across three distinct cropping regions across NW Tasmania, with additional monitoring conducted at one site in Victoria. Data is being collated for analysis with further data to be collected in 2022.
Data on the impact of key foliar diseases was also collected from two replicated trials, each conducted at two sites in the 2021/22. A summary of the data collected is available in the SFT report.
Additionally, a replicated greenhouse experiment was conducted in late 2021 to supplement the data collected from field sites. Plans to duplicate this trial in 2022 is underway.
Work has progressed to focus on the project’s intermediate outcome: Improved understanding of the epidemiology of tan spot and ray blight with specific reference to the environmental conditions that favour outbreaks.
- Field monitoring of fungal diseases in different pyrethrum growing regions was initiated at 21 sites across northern Tasmania and Ballarat in Victoria. The trials are designed to measure regional and climatic impacts on the incidence and severity of tan spot and ray blight.
- Laboratory studies to estimate the impact of temperature and light on fungal spore formation were conducted, with further work planned to provide complementary data to field observations.
- In late winter 2021, research studies to measure the impact of these fungal diseases on pyrethrum crop yield were also started in collaboration with Botanical Resources Australia. A further three sites will be established in October 2021.
- Research studies are planned to continue into 2023 to enable construction of disease risk models for improved and more efficient management of these diseases.
It is now understood that spore formation by the major fungal pathogens of pyrethrum require mild environmental temperatures and that this is enhanced by light. This project will continue to collect data to build on this knowledge over the next 18 months.
This project was a strategic voluntary levy investment in the Hort Innovation Pyrethrum Fund