Glyphosate-resistant brome grass in WA

Jo FulwoodThe West Australian

WA's first strains of glyphosate- resistant brome grass have surfaced on farms in the south of the State.

While glyphosate-resistant brome grass was discovered on the east coast several years ago, WA farmers had so far escaped the problem.

Tests are yet to confirm resistance levels, but researchers at the Department of Agriculture and Food WA believe the lack of response to glyphosate by brome grass in numerous paddocks will mean the start of resistance issues for the industry.

DAFWA senior research officer John Moore said glyphosate-resistant brome grass, also known as spear grass, could become a bigger challenge for the industry than skeleton weed.

He said funding was required to assist farmers eradicate the weed, which is extremely competitive with cereal crops and contaminates the harvested grain, resulting in dockages.

Mr Moore said early seeding and minimum-till techniques favoured the establishment of brome grass infestations.

"Unlike the staggered germination of ryegrass, the bulk of the brome grass germinates soon after the first rains, which is fine if you are cultivating, doing a double knock or planting well after the break," he said.

"However, when you dry seed, you haven't had that first weed emergence or the first knockdown opportunity before the crop goes in the ground, and this is where the weed has had the opportunity to get a stronghold in our environment."

Mr Moore said while other chemical groups could manage the weed, they were more expensive than glyphosate, and resistance issues would mean an added cost burden on the industry.

He said resistant brome grass could also have an impact on crop yields in the long term, limiting varietal choices in affected paddocks.

"If we have glyphosate-resistant brome grass, it's going to cost farmers more money in chemical, or ultimately cost them yield because they will be forced to use varieties that will allow them to use metribuzin to kill the weed," he said.

He said this was a red flag for farmers to closely monitor the effectiveness of glyphosate on their brome grass populations.

"If you had an area sprayed with glyphosate and the kill is poor, it's very important to get that particular patch tested and then make an extra effort to eradicate those plants that carry the resistant gene," he said. Other strategies to tackle the weed include chemical fallows, green manuring, tickle cultivation, weedseed destruction, burning or delayed seeding.

"A combination of these tactics are usually needed to be applied," Mr Moore said.

GRDC projects have identified brome grass as an emerging weed and the recent glyphosate resistance issues meant double trouble.

"Most growers are likely to get glyphosate-resistant brome grass by introduction to their farms as a combination of produce, stock or equipment, so good farm hygiene and biosecurity measures should be the first strategies considered to avoid this emerging threat," Mr Moore said.

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