Many farmers at risk of getting Annual Ryegrass Toxicity (ARGT) may not be aware of the potential spread of the disease.

Western Australia Department of Agriculture biosecurity officer Greg Shea said ARGT already occurred in parts of the northeastern wheatbelt, but there was evidence that the causal organisms are spreading into new areas. 

"The increasing incidence of herbicide resistance in ryegrass in the wheatbelt limits the options for control thus the heightened importance of getting ahead of the problem for farmers in surrounding areas," Mr Shea said.

"ARGT is an acute and often-fatal neurological disease of livestock caused by the consumption of annual ryegrass seed heads infected with a bacterium."

The bacterium is soil borne, but gains access to plants in winter by adhering to the seed gall nematode, Anguina funesta. It colonises the nematode galls and the flowers, and bacterial galls are formed. The bacterial galls remain toxic throughout the following summer and autumn.

Mr Shea said on properties where ARGT has not previously been found peripheral areas such as along fence lines, contour banks and waterways should be checked for diseased plants.

"The nematode and bacteria may be expected to be more abundant in these areas than in the general paddock because the ryegrass in such areas has usually been undisturbed," he said.

"Areas where hay or grain has been brought in and fed out should also be checked."

He said growers could minimise the risk of introducing ryegrass.

"When buying seed or feed, check the level of ryegrass that is present, and clean machinery and vehicles of any soil and plant matter. This will also help prevent the introduction of herbicide resistant ryegrass," Mr Shea said.

"Often, the control of ryegrass in a paddock is very good overall but areas such as rock heaps and fence lines need attention to prevent ryegrass getting out of control and posing a threat to grazing animals."

For many growers, there will be an opportunity to prevent the build up of the nematode and bacterium that cause the problem in ryegrass by applying twist fungus.

Mr Shea said if the nematode was detected early, before ARGT strikes, the twist fungus could become established and take over before the bacterium built up to dangerous levels.

He said twist fungus was useful because it was unlikely that ryegrass could be eradicated, especially with the increase in herbicide resistance among ryegrass populations. Also, some ryegrass-infested areas on farms don't get treated with herbicide.

"Another common question is whether greater use of fungicides in-crop will have an effect on twist fungus establishment," Mr Shea said.

"The way around this problem is to target these peripheral areas on the farm where the twist fungus has the best opportunity to establish.  Fungicide is not usually applied to these areas."

"Twist fungus is applied in May/June of each year and ordered from a commercial provider.  Orders need to be received by 29 February 2004.

More information about where to purchase twist fungus or how to identify the presence of the bacterium and nematode is available from Mr Shea at the Department's Merredin office.