The Crop Doctor
Grains Research and Development Corporation

Pythium has been described as the 'common cold' of cropping and the full impact of its effect on yield is unknown. Now the search is on for solutions to this mysterious root fungal disease, which appears to be infecting an increasing area of cropping land across southern Australia.

There are no obvious above ground symptoms of the disease, only a lack of vigour and reduced yield in cereals, pulses and canola. And as yet, there are no commercially available soil tests, so even confirming presence of the disease is difficult.

Among numerous projects focusing on the disease is a trial that is about to begin on Kangaroo Island, South Australia, which aims to find out what the disease is costing farmers in lost yield and quality.

It will be conducted as part of a project on high yielding and high value crops, supported by the Grains Research and Development Corporation through its Sustainable Farming Systems program. The work will be done on a property south of Parndana, where soil tests by the CSIRO have confirmed the presence of the disease.

Project leader, agronomist Rick Morris, says the trial will also test the effect of using metalaxyl-based seed dressings to protect both wheat and canola from the disease.

One of the theories about the apparent increase of pythium is that it is being aided and abetted by the widespread adoption of reduced tillage or no tillage, so the KI trial will also compare the effects of minimum tillage to burning stubble and conventional tillage on expression of the disease. When the soil is left undisturbed, so are the infected roots from the previous crops, which then infect germinating seeds and growing roots. This restricts root growth, which in turn inhibits vigour and grain fill.

Mr Morris believes pythium could be responsible for the often poor results in paddocks when canola is sown with no-tilling into retained cereal stubble. These crops are often very slow to establish, which predisposes them to damage caused by slugs and Adelium (bronze field beetle larvae). He says this has become the phase in the rotation where stubble burning has become necessary.

Mr Morris says the extent of the disease on the island is unconfirmed but appears to be more prevalent in districts with higher rainfall and acidic soils.

For more information please contact Rick Morris on (04) 2771 5211.