Did you know that there are 513 registered herbicides in Australia that contain glyphosate? It is the most widely used herbicide in Australia, in both agricultural and non-agricultural situations.
It was 15 years ago when the first case of an Australian weed becoming resistant to glyphosate was reported. At first it was a problem for farmers who practised continuous cropping, but it’s now a problem in many different situations; including around buildings, driveways, fencelines, firebreaks, irrigation channels and even an airstrip.
A survey by Dr Christopher Preston of Adelaide University in 2012, showed high levels of glyphosate resistance in 50% of 400 weed samples taken from roadsides in five states. Resistance was found in annual ryegrass, fleabane, windmill grass and barnyard grass. This is not surprising, given the almost total reliance on glyphosate herbicides for roadside weed control in the past few decades.
Glyphosate has been the ‘dream herbicide’ for roadside weed control – it kills almost every weed, does not produce obnoxious odours that annoy the public, and has low toxicity to humans. However, that era may be coming to an end, and all users of glyphosate herbicides must seriously consider (1) ways to delay the development of resistance in weeds, and if we don’t get this right, (2) ways to control weeds in the ‘post-glyphosate’ era.
The Australian Glyphosate Sustainability Working Group suggests that you follow four steps if you suspect you have some weeds that are resistant to glyphosate:
- Eliminate other possible causes of the weeds surviving after you have sprayed them with glyphosate (eg poor application method, or unsuitable conditions when spraying)
- Contact a member of the Australian Glyphosate Sustainability Working Group for advice on how to confirm the suspected resistance
- Prevent the surviving weeds from setting seed
- If resistance is confirmed, develop a management plan for the future, enlisting the help of an expert if required
More information can be found on their website, with resistance management strategies for a number of situations, including grain cropping, orchards and vineyards, and roadsides, railways and other non-crop situations. Go to http://glyphosateresistance.org.au/index.htm