Delving to root of sub clover losses

In severe cases there may be up to 90 per cent plant non-emergence, 40pc non-survival of seedlings and 30pc reduction in dry matter production in sub clover pastures in south-west WA and across southern Australia.

The MacKillop Farm Management Group and the Barossa Improved Grazing Group are hoping to quantify disease levels through germination, seedling emergence, and nodulation scores at local trial sites.

They also hope to come up with cost-effective solutions to reduce impact on new and established stands through various chemical control and cultural methods.

The main soil-borne pathogens that affect subclover include Pythium, Phytophthora, Aphan((xAD))­omyces and Rhizoctonia.

These usually exist as a disease complex that can affect establishment and persistence, reduce germination, destroy roots, reduce plant size and cause failure of nodulation and persistence of pastures.

The two SA farming groups are in the second year of the three-year Meat & Livestock Australia-funded projects through the Producer Research Site Program, and are also working closely with University of WA researcher Martin Barbetti.

MFMG project coordinator Nick Edwards said their first year of research involving producer demonstration sites across the region pointed to 10-15pc reduction in germination and survival of plants from Apron-treated versus non-treated seed.

There was also a 30pc difference between new less-susceptible variety Trikkala and older variety Woogenellup, indicating some level of disease.

In the second year, two trial sites at Furner and Avenue Range had focused on a wider range of seed inoculants.

There have been no significant differences in the six inoculants but there has been up to 30pc variation in the ten cultivars evaluated in the trial.

Trikkala, Dalkeith and Antas have been consistently among the top performers in their seedling establishment and growth three weeks, nine weeks and 12 weeks after sowing.

In contrast a smaller percentage of plants established in older varieties such as Woogenellup, Leura and Goulburn.

Dr Edwards said two consecutive dry years may have reduced the impacts of soil-borne diseases but the group was keen to trial other treatments in 2016 but more importantly trial them on a larger scale than the 100 seed strips or 1 square metre plots to date.

"Sub clover is an important part of our pasture make up. It is good winter feed and nitrogen-fixer for our grasses in the system and if you do have significant levels of the disease you get a browning-off effect, dying sub clovers, and really poor stunted growth as well," Mr Nick said.

"People often comment it is a poor clover year but is it? Maybe it is a poor clover year because there is a whole heap of root disease and other factors at work."