Lessons on root disease in sub-clover

Plant pathologist Professor Martin Barbetti from The University of Western Australia is, along with his research team, conducting trials as part of the Barossa Improved Grazing Group (BIGG) MLA-funded Producer Research Site at Moculta in South Australia.

Recently he spoke at the BIGG Spring Pasture Walk, attended by 40 producers.

Professor Barbetti gave an overview of soil-borne root diseases and outlined the research being conducted to improve the performance of sub-clover pastures. 

Facts already established about soil-borne root disease, he said, included:

• root disease in sub-clover is caused by a range of soil pathogens; particularly pythium, phytophthora, aphanomyces and rhizoctonia, with rhizoctonia being the key root disease occurring locally in sub-clover pastures
• large difference exist between sub-clover cultivars in their resistance to each of the root diseases
• as the incidence of root disease in sub-clover plants increase, nodulation decreases
• good plant nutrition helps limit the impact of root disease in sub-clover
• prior to re-sowing a sub-clover pasture, consider cultivating as this reduces the incidence of root disease
• a long-term solution for managing sub-clover root diseases is breeding resistant cultivars. 

Apart from visiting the sub-clover research trial site at Moculta, participants on the pasture walk inspected BIGG’s nearby watercourse revegetation project (on Murray and Ben Klemm’s property) and a native pasture management project site at Sedan (Joe Keynes' property). At Sedan the results of a trial measuring the effect of superphosphate fertiliser on pasture production and the extent of recovery of native grasses after the 2014 Eden Valley bushfire were observed.

Sub-clover is a vital component of Barossa pasture systems and in 2014 BIGG received a three-year Producer Research Sites grant from MLA for the project, which is run with the University of WA. MLA’s Producer Research Sites program partners producers with researchers to explore if, and how, research fits into farming systems.

BIGG’s 2014 trials were conducted at Moculta and Eden Valley and evaluated the productivity of three different sub-clover cultivars (Clare, Trikkala and Woogenenellup) with and without the fungicide seed treatment metalaxyl. Metalaxyl is registered for the control of seedling diseases caused by pythium and phytophthora in sub-clover but has not been trialled locally.

Treatments in the trials were sown in one metre row plot and assessed for seedling emergence (2-5 weeks after sowing), plant nodulation and dry matter production throughout the growing season. Although soil-borne root diseases were known to be present at both trial sites, the results indicated that no clear conclusions could be drawn on metalaxyl’s effectiveness to reduce the impact of root diseases. This was also complicated by the short growing season, with well below average rainfall occurring in late winter/spring at both sites.

The 2015 trials include further investigations with metalaxyl. They complement a range of similar field research that the University of WA is conducting at a trial site in the Barossa this year. These trials include chemical seed and spray treatments, cultivation and livestock grazing as potential root disease management strategies in sub-clover.

More information: brett.nietschke@biggroup.org.au

For more information on MLA’s Producer Research Sites program, contact Irene Sobotta, MLA E: isobotta@mla.com.au