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Advice from weed resistance expert: try diversity

Renowned weed scientist Steve Powles, having had to find solutions and work-arounds in resistant weed-infested crops in his native Australia, has tried to prepare American producers for their own burgeoning resistance problems.

In 2005, just as glyphosate-resistant pigweeds began to tighten their grip on fields in the American South, Powles cautioned U.S. producers against continuing practices that would only spread resistance.

“There is something Australia is No. 1 in the world at: herbicide resistance. We know about this problem and have the dubious distinction of being tops. However, the United States is about to take the top spot away from us. My prediction is you will be crowned king of herbicide resistance within the next few years.” (Read more here)

In summer 2013, Powles again visited the United States and his message took on a more urgent tone. Agronomic diversity is a must, he told Farm Press, if American producers are to head off massive cropland problems.

Here are comments from the Q&A:

It’s been several years since you were in the States. What have you been doing on this trip?

“I’m participating in seminars and the like. I began with a tour through the Texas High Plains, checked out the Arkansas pigweed situation and then headed to Illinois. That was a great opportunity to speak with many farmers, agronomists, crop consultants and university people.

I’ve spent a few days at the University of Illinois Champaign-Urbana and a day at a weed resistance symposium in Indianapolis.

“Looking at the situation in the field, talking with farmers — which is always great, because I have my own farm in Australia —and all the rest has made for a fantastic trip.”

A few weeks back, University of Illinois Weed Scientist Aaron Hager was saying Illinois’ biggest problem is still waterhemp but pigweeds are becoming a larger issue (read here). Have you noticed that shift?

“Yes. Two years ago, pigweed had become a real problem in the South. That has only spread farther afield.

“When I was visiting the Texas High Plains, they told me resistant pigweed wasn’t a problem in 2012. This year, though, it’s in as much as 50 percent of the fields.

“That’s just the exponential part of the curve, which states like Arkansas, Mississippi and Georgia have been through. Whereas, in the Midwest, the Corn Belt, the producers have had a different set of issues.

“I don’t want to overstate the situation, but on a bus ride from Chicago to Indianapolis — with many stops — you can really see a sprinkling of marestail and waterhemp through some 50 percent of the soybean crops. I’m prepared to claim that those weeds are glyphosate-resistant. Those aren’t just misses. I don’t remember seeing that several years ago.”

What about new soybean technologies?

“I’ve seen some of that. The 2, 4-D-tolerant soybeans are most impressive, actually.

“I hope none of the new technologies are clear ‘winners.’ I say that because if I was a U.S. farmer and could use Monsanto’s glyphosate and dicamba-tolerant soybeans, I’d use them. And then, I’d leave them alone for a few years. Same with Dow’s glyphosate/2,4-D-tolerant technology. Same with Bayer’s LibertyLink crops.

“Get the picture?

“These things offer diversity to the farmer. And they must be protected. Which producer wants to be in Delta Farm Press for being the first one with glufosinate/LibertyLink-resistant weeds or dicamba-resistant weeds or HPPD-resistant weeds?

Well, if they want that, if they want a photo in your publication, they can just keep planting the same thing over and over. The resistance will happen.

“Anyone who wants these technologies to keep going, if they want to keep a good thing, then they must change things up regularly.”

On resistance in Australia…

“We’ve learned the hard way that you cannot simply rely on the next jug. It’s simply unsustainable — you waste the chemicals’ efficacy.

“I love herbicides. I reckon they’re the best way to control weeds in cropping. But they aren’t much good if they don’t work.

“And the only way to keep them working is diversity. That means employing non-chemical techniques as well as smart rotation of chemicals and crops.

“We’ve learned that we must do ‘harvest weed seed control.’ That involves non-chemical, mechanical techniques at harvest.

“When I suggest that in the United States, everyone looks at me and thinks, ‘I’m not doing that.’ I can see it in their eyes, I can see them working it over in the minds: ‘We won’t do that.’

“But you know what? They’re already doing that when they march the hand-hoeing teams across the cotton fields. What they’re doing is practicing very, very expensive harvest weed seed control!”

On the objective of his trip…

“I’m here to help convince everyone involved in agriculture that they should think about harvest weed seed control. But it’s tough because people simply aren’t psychologically ready for that. All the creativity is still aimed at reaching for the next product.

“I hope everyone doesn’t have to learn hard lessons before considering these other techniques.

“But let’s not get depressed about this. It doesn’t have to be this way. We can manage the problems if we’d just be more diverse and pay more attention to agronomy and rotation.

“We wouldn’t be farming in Australia if what I’m saying wasn’t true.

“Fortune favors the prepared mind. You must actually do something more creative than reaching for the next jug.”

Is that a uniquely American mindset?

“No. It’s simply due to the fact that, until recently, there have always been new herbicide solutions.

“You know, ‘There’s a problem? Well, let’s just move on to the next product.’

“That’s been the experience of nearly everyone in our industry. Well, those days are coming to an end and change will come because it will be forced. Multiple herbicide resistance in waterhemp, pigweeds, marestail and johnsongrass is no joke. Control is not easy.

“However, control can be achieved with real attention and effort. I’m afraid without that focus, farmers will go bankrupt.”

On the ‘zero tolerance’ efforts (more here) in the Mid-South…

“I’ve been following that. That’s exactly the sort of thing that’s needed.

“I met with an excellent farmer, David Wildy, of Manila, Ark. On his land, he has very low pigweed numbers. That’s due to zero tolerance, doing what he must. He’s demonstrating success.

“And I’m willing to bet that if you talk to him, he’ll say zero tolerance is a pain in the neck. But he’s done it and made a success of it.

“I was speaking to another Arkansas farmer and said, ‘You can get on top of those Palmer pigweeds.’ He said, ‘Steve, at the moment, pigweed is like my mistress. I think of her when I wake in the morning, throughout the day, and then just before I go to sleep.’

“I thought that was pretty good. But that’s the focus you need to control a formidable opponent.”

On the importance of dealing with the soil’s seed bank…

“Say you’ve got a big cotton field, a Roundup Ready variety, and you’ve got a grown-up mess of glyphosate-resistant weeds. In that situation, simply switching to an alternative technology is a bad idea.

“What you must do is get your seed bank of those resistant weeds low. It seems that many people don’t understand the concept of a seed bank. Get the numbers low enough and your precious herbicides are much more sustainable.

“If farmers would understand that and practice it, they’d be much better off.”

This article was published online at Delta Farm Press.

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