Land and Water Link

16 - May 2004

Disease Control, Nature’s Way

A new range of natural options for disease control may soon be available to farmers all over the world – and CSIRO Land and Water is at the forefront, with international research into new ways to increase crop production through biological control.

As team leader Dr Maarten Ryder explains: ‘Biocontrol options have long been available in horticulture – for growing fruit and vegetables. The best example is the treatment for Crown Gall disease, which has been around for more than 20 years.

‘In contrast, farmers in broadacre agriculture – with big farms under annual cropping or cropping/grazing rotations – have really missed out. These products have tended not to be available to them at all.’

Now, thanks to CSIRO research, wheat and barley farmers may soon be able to use natural biological inoculants to control soil-borne root diseases such as Take-all.

The Take-all fungus infects the roots and restricts the uptake of water and nutrients, causing extensive damage to the plant. ‘It usually occurs in patches, with typical grain losses in the region of 20-50%, but in very severe cases the disease used to claim the entire crop’, says Dr Ryder. ‘The cost to the industry is around $50 million per annum.’

However, other micro-organisms have been known to suppress Take-all in natural systems. The beneficial effect of a particular isolate of Trichoderma koningii was first discovered in disease-suppressive soils more than a decade ago.

‘That discovery was made by Andrew Simon, who started his working career as a CSIRO technician and went on to complete a PhD at the University of Western Australia’, recalls Dr Ryder.

‘During his PhD he isolated these strains of Trichoderma that could attack the fungus that causes Take-all. And when he came back to Adelaide he did some tests to show this organism could control disease.’

It was the beginning of a collaborative research project that would extend across the globe, supported by the Australian Centre for International Agricultural Research (ACIAR).

‘Since 1994, various different bacteria and fungi isolated from soils in Australia and China have been tested for their ability to control target root diseases in wheat, cotton and vegetable crops. But Trichoderma has remained the prime focus of our research.’

Dr Ryder believes that the best examples of biocontrol tend to come out of ecological studies, as opposed to mass screening projects (where you simply test a huge number of the bugs in the soil in the hope that some of them will have the potential to control a particular disease). ‘Mass screening is like looking for needles in haystacks. It’s better to know something about the haystack and whereabouts in the haystack you might find it, rather than just saying “Oh well let’s go look in the haystack and maybe we’ll find something”.

‘So that’s what I like about Andrew’s work; it was based on ecological knowledge. And the development of biocontrol for Crown Gall disease came from ecological knowledge too.’

CSIRO’s Trichoderma has been thoroughly tested in over 50 field trials across Australia, USA, China and New Zealand during the past 15 years.

In Australia, the yield response has been shown to be equivalent to that achieved with a chemical pesticide currently on the market. And a Chinese formulation developed in 1998-99 was made available for small-scale commercial testing.

‘Now the commercial potential for an Australian product is currently being evaluated by Bio-Care Technology and CSIRO, in collaboration with researchers in China’, says Dr Ryder. ‘Bio-Care Technology already sells inoculants such as Rhizobium, which is used to establish the nodules on legumes that fix nitrogen.’

Trichoderma has also demonstrated potential for the control of other plant root diseases, such as Rhizoctonia root rot on barley and ‘pineapple disease’ in sugarcane.

‘The next step is really to multiply this little bit of the soil biota (to increase the number of active organisms) and then put it into a form that the farmer can use, like a seed coating – and do it all in a way that is economically viable.

‘The connection with China is really valuable. I’m really grateful for the extra funding that we have for commercial development from the Australian Government Department of Education, Science and Training’s Industry Assistance Program, as it has allowed us to travel and work very closely with our colleagues at the China Agricultural University, Chinese Academy of Agricultural Sciences and Zhejiang University.’

CSIRO Contact:
Dr Maarten Ryder
Ph: +61-8-8303 8534