Macca's Musings - How Herbicide Resistance Can Occur

24 Sep 2024. Paul McIntosh, Pulse Australia and WeedSmart.

There's no doubt that our farming systems have developed greatly over the last 40 odd years and I know because I have been along on that long ride. Also without doubt if we were farming the same way from the 1960 and 70's, our productivity and arable cropping lands would be heavily reduced.

In those early 1980's, newer farming techniques came along with terms like minimum or zero tillage summarised as conservation farming. Also as we all know, is the huge increase in herbicide use patterns both in-fallow and in-crop. The biggest mode of action we have applied over these decades is Glyphosate and of course, it is now one of our biggest products to develop herbicide resistance in many of our weeds or plants out of place.

Way back in the late 1980's a new knockdown herbicide called Basta with the active ingredient Glufosinate was brought into Australia by the Hoechst company. With its big $ per hectare cost and lack of wide spectrum control levels, myself and many others left it on the sideline thinking it will never take off here in our Aussie conservation farming practices.

Well how wrong was I, as we fast forward to 2024, and this different mode of action to Glyphosate herbicide is now on the front line with several different names like Biffo from Nufarm.

That's the history lesson - now for a modern day reality check on the Glufosinate doorstep, with potential herbicide resistance in the future. This Group 10 (was N) mode of action herbicide is now much more widely used due to several farming system factors.

What I would like to point out is the potential for herbicide resistance, specifically target site resistance mechanism which could occur. Like other target site mutations as Peter Newman from Weedsmart in WA explained to me, our very smart AHRI colleagues in Perth have discovered how resistance will develop for Glufosinate. They have done this by a common lab technique in rice, which they have even given a name - Ser59Gly mutation.

So what does this all mean for us in Queensland and Northern NSW? It means that we now have knowledge that the more popular Glufosinate product can develop herbicide resistance in our farming systems - it is not bullet proof.

What we all have to do differently from the last 40 years from our popular Glyphosate use patterns is too follow the WeedSmart Big 6 edits. Most importantly is that anytime after applying this Glufosinate product, ensure there are no survivors that could set seed.

I could add a quote my father Alec said to me many years ago, when I got up to do a formal weed presentation in his and many others' presence. "Don't stuff it up" were his words to me. Fairly nerve calming that wasn't at the time.

My thoughts and words to all the users of Glufosinate in our 2024 farming systems are the same - let's not stuff it up with this herbicide Glufosinate unique mode of action.

That's all folks.

Regards, Paul McIntosh (JP Qual)

Plenty of herbicide resistant Annual Ryegrass on fence lines around the Northern region.

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