Ryegrass is a serious problem for growers with post-emergent herbicide resistance and a wet season limiting spray opportunities to combat it, 2022 was a "nightmare year".
Subscribe now for unlimited access to all our agricultural news
across the nation
$0/
(min cost $0)
or signup to continue reading
Constant wet weather in many areas of the state gave ryegrass a predominantly free pass last year with late germination rendering herbicides inefficient.
Alectown grower Neil Westcott said they had a particularly bad year for ryegrass.
Mr Westcott, his wife Alison and son Hayden grow winter crops on their 2100-hectare property Swansea, growing mainly wheat, barley and canola.
"Ryegrass got away from us a bit last year," Mr Westcott said.
"It was quite prevalent not only on our property, but in the area as well. I see it as one of the biggest threats to continuous cropping.
"With the resistance levels, most post-emergent herbicides are basically useless. May as well put water on it."
Mr Westcott said he was hopeful for more opportunities for spray control.
"I'm going to have to use all the tools in the bag to get on top of it," he said.
"Hopefully the season allows us to get on and spray. With post-emergent herbicides largely ineffective, I'll rely upon pre-emergents and post sowing pre-emergents.
"I will be double-knocking using glyphosate first and then paraquat.
"The first lot of ryegrass is shooting now, along with some other winter weeds, which is good. It is easier to manage early on."
ALSO READ:
Mr Westcott said he will be looking at what he can do to minimise his ryegrass exposure in the future.
"Keeping seed carryover down will be important," he said. "I think I will have to start windrow burning."
Chris Preston, professor of weed management at the University of Adelaide, was part of a research group which ran a national resistance survey with results in NSW ringing the alarm bells.
Nearly one quarter of annual ryegrass samples in NSW were resistant to glyphosate and resistance to Group 1 and 2 post-emergent herbicides was widespread.
In the summer of 2020 - 2021, the survey covered the whole of the Australian grain region, all at once, using the same methodology so they could compare what was happening in Western Australia to what was happening in NSW.
"Nationally, there were about 1600 paddocks surveyed with 13,000 samples tested to 12 different herbicides," professor Preston said.
"Looking at post emergent herbicides in NSW we had 317 samples and in annual ryegrass, resistance to the Group 1 herbicide Axial was high with 73 per cent of samples collected in NSW resistant.
"Resistance to the Group 2 herbicides was high with 86pc of samples collected in NSW resistant to Hussar and 67pc resistant to Intervix. But what we are also seeing is a growing resistance to glyphosate (Group 9) with 23pc of samples collected in NSW resistant to this herbicide."
Professor Preston said there was still an effective way to manage ryegrass.
"Resistance to pre-emergent herbicides was less frequent," he said.
"No resistance was identified to Sakura (Group 15), Rustler (Group 3), Luximax (Group 30) or Overwatch (Group 13).
"Pre-emergent herbicides are likely to be still effective for annual ryegrass control, where post-emergent herbicides are increasingly likely to fail."
