Australian Herbicide Resistance Initiative (AHRI)

Blog: AHRI insight

Windrow burning

Australian Herbicide Resistance Initiative (AHRI)

Windrow burning – a good place to start

The best option to maximise the weed seed bank is to harvest high and spread all of the weed seeds evenly over the paddock. This will give you something to spray next year. If you, like most others, feel that this is a bad idea, it may be time to start narrow windrow burning. Narrow windrow burning is a good place to start to see if this harvest weed seed control caper is all it is cracked up to be. The first step is to spend some time familiarising yourself with a beer can. The internationally accepted harvest height when…

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Ryegrass growing boxes on tables

Australian Herbicide Resistance Initiative (AHRI)

Creating a cross resistant monster

Are the wheels falling off the concept of herbicide rotation to manage resistant weeds? In recent years new ryegrass herbicides have been released, giving us some hope that there will be a herbicide solution to our problems. Imagine if your ryegrass was resistant to one of these fantastic new herbicides the first time you used it. We have seen this in the past and we may be about to see it again. AHRI researcher Dr Roberto Busi has previously shown us that low herbicide rates is not good practice as it can lead to faster resistance evolution for some herbicides….

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woman working in lab

Australian Herbicide Resistance Initiative (AHRI)

More resistance = more dormancy

If you drove to work at the same time each day and hit a major traffic jam each time, you might consider changing the time you drive to work. It seems that annual ryegrass has also come to the same conclusion. AHRI research by Mechelle Owen has confirmed that greater seed dormancy is positively correlated with higher levels of herbicide resistance in ryegrass. That is, populations of ryegrass with a higher resistance status had higher levels of seed dormancy, and although these traits are not genetically linked, it does allow ryegrass to germinate later to avoid knockdown (burn down) herbicides….

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Machines plowing field

Australian Herbicide Resistance Initiative (AHRI)

To win the war you must win the battles

As Darkan farmer and inventor of the Harrington Seed Destructor, Ray Harrington, aptly says, “Harvest weed seed control is a pain in the ….” – but it is an imperative tool in continuous cropping systems”. “To win the war you must win the battles. Harvest weed seed control is an important battle. If you’re not implementing weed seed control at harvest, you’re out of the farming game”. It’s a tough message to hear, and it’s one that growers from Wagin, Lake Grace and Ravensthorpe in Western Australia heard at AHRI’s “More crop, less weeds – sustainably!” workshops last week. The…

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Grass

Australian Herbicide Resistance Initiative (AHRI)

Pollen flow of resistance genes

“It wasn’t me, it was him!” Many grain growers blame their neighbours for developing herbicide resistance. Growers often feel helpless! Regardless of how well you manage your weeds, unfortunately it is inevitable that you will inherit the resistance problem from your neighbour. It is true that resistance genes can flow a long way in pollen. AHRI researcher Dr Roberto Busi demonstrated that ryegrass pollen can travel up to three kilometres. More research in theUShas shown that gene flow via pollen varies between species, depending on the level of out crossing and pollen characteristics. It is no surprise that the resistance…

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Weeds sample in glass

Australian Herbicide Resistance Initiative (AHRI)

How do weeds resist glyphosate?

If you ever find yourself in the situation where you are catering for a group of people, and you are wondering how much food to prepare, the best thing to do is to prepare a little extra, just in case. The last thing that you want to do is run out. Believe it or not, this is how some weeds resist glyphosate. They make an extra-large batch of the enzyme that glyphosate binds to, just in case. This way, if the weed is sprayed with glyphosate that inhibits some of the enzyme, there is still enough left for the plant…

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Man touching a plant

Australian Herbicide Resistance Initiative (AHRI)

AHRI Mythbusters – can 2,4-D induce resistance in ryegrass?

What if you accidently sprayed the wrong herbicide? Agronomists of yester-year developed a handy trick. They found that if they accidently sprayed an oat crop with Hoegrass® (diclofop-methyl), they could stop crop damage in its tracks if they quickly applied 2,4-D. The grand question is…does it actually work? The ‘myth’ says yes. What does the science say? The AHRI Mythbusters team got the answer! In this latest AHRI research, Dr Heping Han and others found that when they pre-treated ryegrass with 2,4-D amine it became resistant to Hoegrass®. This is likely due to 2,4-D causing a spike in P450 activity…

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Researcher looking at samples

Australian Herbicide Resistance Initiative (AHRI)

How do P450 enzymes cause resistance?

What is a P450? Is it a car from the 70’s that fits a 44 gallon drum in the boot? No, that would be a P76. A P450 is an enzyme that eats herbicides. In fact, there are literally hundreds of P450 enzymes and some of them can chew on some herbicides, resulting in enhanced herbicide metabolism (metabolic resistance). We are now seeing an increased effort around the world to better understand metabolic resistance involving P450 enzymes. In 2005, Dr Paul Neve showed that ryegrass could quickly develop resistance after being sprayed with low doses of Hoegrass® (diclofop). Some recent…

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Glasshouse with plants

Australian Herbicide Resistance Initiative (AHRI)

Too cold for glyphosate resistance

Most of us are a bit slow out of bed on a cold morning and take a little while to get moving. Weeds are no different. Some glyphosate resistant weeds become less resistant in cool weather. One of the mechanisms of resistance to glyphosate is to reduce the movement of the chemical through the plant (known as translocation). Researcher Dr Martin Vila-Aiub and others from AHRI tested annual ryegrass and Johnsongrass with this resistance mechanism. They found that the plants were much less resistant to glyphosate when the plants were grown in cool conditions. The good news? If you know…

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Wild radish flower

Australian Herbicide Resistance Initiative (AHRI)

Is there a fitness penalty in Group B resistant weeds?

When we talk about the fitness of weeds, it’s not about how fast they can run a marathon. We are talking about how well they grow and how many viable seeds they produce. Weeds with fitness penalties just don’t grow and reproduce as well as they should, even in the absence of herbicides. Are there fitness penalties for Group B (e.g. Glean®; ALS inhibitor) resistant wild radish? Visiting researcher, Mei Li, along with other AHRI researchers, set out to answer this question. Unfortunately, the answer is NO! Wild radish, with four different target-site ALS mutations, were equally as fit as…

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