Rhizoctonia Disease Management Following Pasture

Chris McDonough, from Rural Solutions SA, demonstrates how to identify the root disease, Rhizoctonia, and how to manage your paddocks to minimise it’s effects.


Chris McDonough from Rural Solutions SA, demonstrates how to identify the root disease Rhizoctonia, and how to manage your paddocks to minimize it’s effects. The project was designed looking at paddocks. First of all in 2010 we had 2 pasture paddocks. One was a really good medic pasture, it had about 25 percent barley grass in it, so we divided that up with the farmer equipment, would say half was spray-topped, and the other half was grassed removed.

Rhizoctonia Levels

We followed the Rhizoctonia levels right through to seeding time in May, We actually found that generally, the area that was grass removed had low levels of inoculum in the soil, and the areas that were only spray topped had medium levels of inoculum in the soil, so there’s quite a difference there, and very consistent difference between all the plots that we  did.

But it was also interesting that the farmer actually missed spraying out some of that grass that had germinated in February in a few areas, and we actually tested those areas as well, and found that those areas were sky high with Rhizoctonia. The thing with Rhizoctonia is that, you know, it can be sitting in the soil, but once the season starts, we gets some rainfall, the soil gets a bit cooler in autumn, then it really starts to grow out from it’s spores and into, and if it can latch onto anything growing then, then it will start to build up and can build up quite rapidly.

Some of the ways that farmers can actually find out that they have Rhizoctonia, obviously if you go out into a crop situation like this where you see poor patches, dig down, you wash the roots out in some water, have a close look, and there’s plenty of guides around where you can tell okay well that’s clearly Rhizoctonia, or you might have other issues like CCN or things you can identify.

Some Examples

Here’s some examples in a fairly poor plant of classic can Rhizoctonia spear tipping, and certainly you can see that, and even up here, and right through to some of this plant here which is a more mature plant and this is more I guess some of the secondary roots which obviously shortented, have been affected The other thing that’s really good is the root disease testing service, which you can do that allows you then get them an idea of a whole lot of diseases, what the inoculum is in the soil going into that cropping season and whether those levels are a high enough risk that you actually need to do something to manage that if you came back with a high level, obviously, keeping that ground volunteer weed free is very Important because that can certainly inhibit the build up of Rhizoctonia things like the nutrition you use in your crop maybe using more zinc with helps strengthen cell walls in the seedlings. Things like Group B herbicides which, again, can impact on early crop growth and affect roots. You know, anything that’s going to impact badly on the roots is going to advantage Rhizoctonia. The roots give you an idea of what inoculum in the soil but your management from there can have a big impact on whether that becomes a big issue in your crop or not.