Annual ryegrass toxicity is taking its toll, costing livestock producers about $40 million a year according to Department of Agriculture and Food estimates.

Along-side chemical control of ryegrass, three biological control options - Safeguard ryegrass, Twist fungus and non-toxigenic Rathayibacter are showing the best chance of success.

Contracted on a project funded by Meat and Livestock Australia (MLA) Department development officer David Kessell will present the options to producers at the Department’s Sheep Updates on 13 July, sponsored by MLA and Australian Wool Innovation Ltd.

Annual ryegrass toxicity (ARGT) is a disease of grazing livestock resulting from the ingestion of annual ryegrass seed-heads infected by the toxin forming bacterium Rathayibacter toxicus. 

Mr Kessell said the causal organisms of ARGT were spreading throughout Western Australia after first appearing near Gnowangerup in 1968.  

“Recent surveys have shown the organisms are now widely spread in the wheatbelt and mixed farming areas where annual ryegrass is present,’ he said. 

“Deaths have also occurred on the Swan coastal plain in animals fed locally- produced hay.

“But, while the major visual impact is livestock deaths, this only accounts for approximately five per cent of the overall costs of the disease.  There are subclinical effects on wool and reproduction and suspected on meat production and feed conversion efficiency. 

“Daily monitoring of stock is costly and psychologically draining on producers. There is also a large cost to export hay producers through rejection of contaminated hay (currently from 1 bacterial gall/kg of hay).” 

Mr Kessell said in winter, a number of herbicide options were available to reduce the ryegrass populations in crops and pastures.  The sowing of Safeguard ryegrass was also a very useful option for graziers.

In spring, the use of slashing or heavy grazing to remove infected seed-heads before toxicity developed could vastly increase the safety of affected paddocks.  Spray-topping with gramoxone or glyphosate at the correct times would also prevent further development of toxicity and make paddocks safer to graze, but both these treatments were very damaging to legume seed set. 

Mr Kessell said an integration of several biological control options was likely to have the most success.

“Safeguard is a cultivar of ryegrass that has resistance to gall production from the nematode Anguina funesta.  For Safeguard to have the greatest impact, it must be established in at least a 3:1 proportion with the local ryegrass,” he said. 

“Twist fungus (Dilophospora alopecuri) competes with the bacteria for the nematode vector and plant host.  Inside the ryegrass, twist grows more rapidly inhibiting nematode and bacterial gall production.  Once established, twist will persist and spread, has been shown to dramatically reduce numbers of toxic bacterial galls, and is not adversely affected by commonly used fungicides.” 

“Even though there has been a late start to the season, anyone who has purchased twist fungus should put it out as soon as possible to ensure the greatest likelihood of successful establishment.  It won’t keep until next season.” 

Mr Kessell said the combined effectiveness of the two approaches was demonstrated at a number of sites around Western Australia in 2005. 

“In a particularly impressive case, on a farm near Beverley WA, the treatment reduced toxic gall numbers from potentially deadly to relatively safe, within one season,” he said. 

Non-toxigenic Rathayibacter is a non toxin producing species of the bacteria which is being assessed in quarantine studies and may prove to be highly effective in the control of ARGT.  These bacteria grow more rapidly and have been shown to displace the toxic bacteria.

A decision from AQIS to allow field trials is hoped for by the end of 2006.  Potentially these bacteria would be easier to mass produce and apply than twist fungus.