Scientists at the EH Graham Centre, Wagga Wagga, are looking beyond traditional herbicides for annual ryegrass control in winter crop production.

Two major projects are underway, focusing on allelopathy, the study of chemical interactions that occur between plants in a plant community.

Plants protect themselves by exuding or emitting chemicals that deter insects or inhibit the growth of neighbouring plants.

Many modern plant varieties have had their allelopathy capability accidentally bred out of them.

However, recent research in the United States has produced rice varieties that largely control particular weeds, such as barnyard grass.

One of the EH Graham Centre projects is looking at wheat varieties which are able to exude chemical compounds that can inhibit the growth of ryegrass seedlings.

Dr Hanwen Wu has tested more than 450 varieties of wheat and the work has shown there is considerable potential to select varieties that would exercise significant control over annual ryegrass.

Some of the tested wheat varieties produced close to 100 per cent inhibition of root development in annual ryegrass.

The second project is looking at chemicals contained in plant extracts as potential new "natural" herbicides for annual ryegrass.

According to EH Graham Centre scientist, Jim Pratley, the advantage of this approach is that it deals with natural products, which are normally short-lived in the environment and therefore have desirable environmental characteristics.

"We hope to find new modes of action to complement those that exist for annual ryegrass control," he said.

"So far, we have looked at more than 200 plant species."

Annual ryegrass remains the worst weed of winter crop production in Australia.

It is estimated to infest between 12 and 15 million hectares of crop, costing more than $350 million a year in control measures.

It is world’s worst example of herbicide resistance, and has developed resistance to almost every herbicide used against it.

One project is financed by an Australian Research Council Discovery Grant and the other by the Grains Research and Development Corporation.

Contact Jim Pratley, Wagga Wagga, (02) 6933 2862.