According to Eric Koetz, NSW DPI weeds research agronomist the majority of agronomists and a growing number of farmers recognise the need to implement management practices that help protect the efficacy of glyphosate in farming systems.  

“We know that it takes between 14 and 19 years of routine use of glyphosate to evolve resistance,” Mr Koetz said.

“We have now had Roundup Ready cotton for 15 years and there are many instances of glyphosate resistant populations of weeds such as fleabane, windmill grass and barnyard grass,” he said.

“The 2 + 2 + 0 strategy developed in the cotton industry to protect glyphosate and Roundup Ready technology is also applicable to other farming systems.”

“When planning an integrated weed management program, the Cotton RDC recommends including two non-glyphosate tactics in-crop, two non-glyphosate tactics in the fallow and ensuring zero survivors.”

According to Weed Smart this is where the use of residual herbicides can play a part, along with non-herbicide tactics, such as strategic tillage in both summer and winter crops and in fallow situations. Including residual herbicides in both the fallow and crop phases increases the diversity of herbicide modes of action and places downward pressure on the weed seed bank.

“Roundup Ready technology has been of great benefit to the cotton industry, and has a fit in other farming systems too, but it cannot stand alone. It must be supported and protected through an integrated weed management strategy,” Mr Koetz said. 

“To preserve glyphosate it is necessary to reduce the total number of applications across the crop rotation,” he said.

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