Grower experience shows resistance can be managed
The experience of John Flannagan, who farms with his brother Mark near Mullewa in Western Australia’s grainbelt, is a case in point that glyphosate resistant annual ryegrass can be successfully managed.
“If you can find glyphosate resistant weeds you can manage them,” said Mr Flannagan, who in the last 15 years has twice found patches of glyphosate resistant ryegrass on properties that they own or lease.
“We are now confident that if we find glyphosate resistant ryegrass on other parts of our farm we can beat it, but generally our farm is now pretty clean for ryegrass because of the weed management approach we have taken.”
A big part of the Flannagans’ program is chemical fallow, in which glyphosate is used, followed by a WEEDit detection sprayer to clean up any survivors and hard-to-kill weeds.
“In the early 2000s and then again in 2009 we found patches of glyphosate resistant ryegrass on two different properties,” Mr Flannagan said.
“The area where resistant ryegrass was found in the early 2000s did have a history of chemical fallow, but the 2009 paddock did not.
“However, in both cases chemical fallow was the farming system that allowed us to find these glyphosate resistant weeds because it was easy to find green patches in the middle of a brown paddock.”
The Flannagans’ response, in both instances, was to jump hard and early on the problem.
“We smashed the weed seedbank by using paraquat; crop rotation; some cultivation at times (for the first paddock); narrow windrow burning; robust pre-emergent herbicide mixes in our crops; and never letting ryegrass set seed,” he said.
“Resistance is not a problem where there are no weeds.
“On heavy country that won’t blow, we have used a Grizzly plough to incorporate lime. Herbicide followed by the Grizzly gives us the ultimate ‘double knock’.”
Mr Flannagan said that where glyphosate resistant ryegrass was found in 2009, they initially hit the survivors with high rates of Spray.Seed® (paraquat and diquat) sprayed at night.
“The paddock went to triazine tolerant canola in 2010 and the combination of atrazine prior to sowing and clethodim post-emergence did a good job, as not much clethodim had ever been used on this block,” he said.
“It was sown to wheat for three consecutive years from 2011, with good pre-emergent herbicide application, paraquat knockdown and narrow windrow burning at harvest.
“The paddock went back to fallow in 2015 and there was no ryegrass in this fallow.”
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