Red brome confirmed resistant to glyphosate in Western Australia

One population of red brome (Bromus rubens) has been confirmed resistant to glyphosate in the central wheatbelt of Western Australia. 

close-up photo of weeds

Red brome with giant brome in the background. 

Photo by Agronomo.

This is the first red brome population to be confirmed resistant to glyphosate in the world and is the third glyphosate resistant grass weed species found in Western Australia.

“This finding is of particular concern for no-till farmers who rely heavily on glyphosate for grass weed control prior to sowing and in non-crop areas such as fence lines and firebreaks,” Department of Agriculture and Food, Western Australia (DAFWA) researcher Abul Hashem said.

Dr Hashem and DAFWA’s Catherine Borger discovered the glyphosate resistant red brome under a Grains Research and Development Corporation (GRDC) funded project also involving the Australian Herbicide Resistance Initiative (AHRI).

Dr Hashem says growers must be even more vigilant in their autumn and spring weed control because resistant seedlings of this weed species were found that can withstand up to four times the normal rate of glyphosate.

The glyphosate-resistant red brome biotype was discovered in a long-term trial site where since 1999 DAFWA weed scientists have studied weed population dynamics in response to long-term use of low and high label rates of glyphosate.

“Although the resistant biotype was found in a long-term trial site, the treatments mirror those commonly used by farmers to control weeds on fencelines,” Dr Hashem said.

The closely related giant or ripgut brome (Bromus diandrus) has already evolved resistance to glyphosate in South Australia and Victoria.

While red brome is not currently a major grass weed in WA, it is widespread in paddocks and often found in fire breaks and along fences. Glyphosate-resistant brome populations have the potential to become a significant problem. 

“Even though other brome grass species have developed resistance to Group A and B herbicides in WA, a number of herbicides from Group C, D, J, K, L and N are available to control this weed,” Dr Hashem said.

two pots of weeds; the left is thriving, the right is withered

Red brome plants treated with 4 L/ha glyphosate (540 g/L) at the Merredin Dryland Research Institute showing the glyphosate-resistant population (left) sampled from a long-term trial where low and high rates of glyphosate were applied for 11 years, compared with a susceptible population (right) sampled from nearby unsprayed waste land. 

Photo by Catherine Borger.

“Weed management practices must include rotation of crops with herbicides applied at full label rates and use of non-chemical weed control practices to delay further resistance development.

“Growers who find any brome grass plants surviving herbicide application should send samples to DAFWA or commercial services for a ‘Quick Test’ in which plants are tested for herbicide resistance.

Landholders who suspect glyphosate resistant weeds on their property or roadsides should contact their relevant state expert and their council. Details of who to contact in each state are available from the Australian Glyphosate Working Group website http://www.glyphosateresistance.org.au/suspect_glyphosate.html

For more information on managing glyphosate and paraquat resistance visit the AGSWG web site www.glyphosateresistance.org.au

Information about sustainable integrated weed management (IWM) practices is available at www.ahri.uwa.edu.au

For information on herbicide sustainability visit the WeedSmart information hub at www.weedsmart.org.au

GRDC Project Code DAW535, DAW713, DAW00114, DAW00158, UWA00146

Region National, West