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Pigweed War

Industry Developing Plan To Fight Resistant Weed

By Tommy Horton


Cotton producers have plenty of battles to deal with on the farm every day. Some are small. Some are big. And some are becoming very serious. No matter what may have been said in the past, take it from a couple of weed experts. The resistant Palmer pigweed issue is rapidly taking center stage throughout the Cotton Belt.

When Georgia Extension agronomist Stanley Culpepper first discovered resistant pigweed in 2004 in his state, he was concerned. You might say that he and his colleagues are more than concerned now.

The outbreaks were confirmed in 2005, and in each subsequent year the resistant weed was also found in South Carolina, North Carolina, Tennessee and Arkansas.

He and North Carolina weed science Extension specialist Alan York are at the forefront in identifying, researching and making recommendations to cotton producers about this new threat.

“This is easily one of the major issues that we continue to face in our state,” says Culpepper. “It took about a year to a year and a half before some producers believed the problem existed. Now they’re convinced and interested in dealing with it.”

The spread of this resistant weed has been rapid through traditional means such as custom harvesting, lack of cleaning equipment and infested materials such as gin trash, but it is likely moving most rapidly via pollen.

Besides incorporating different chemistries in spraying, many producers are also cultivating more than ever before.

Implementing A Proactive Strategy

Most Georgia producers are taking the hint and trying to be proactive in their strategies. They’re tankmixing herbicides and implementing various rotation programs – all in an effort to prevent resistant pigweed from even getting a chance to spread.

That’s the good news.

The bad news is that the weed resistance problem is spreading. There are now 10 to 15 times more acres infested with resistant pigweed as there were in 2005, according to Culpepper. The spread of this troublesome weed is reminiscent to the way resistant marestail was first detected in West Tennessee in 2002 and 2003. When pollen is blown several miles by the wind, it can be a daunting challenge to control the outbreak.

“Once you get this weed in your fields, it gets complicated,” says Culpepper. “The first question is, are you irrigated? If you are, you’ve got a chance. If it’s dryland and you don’t get any rain, residual sprays applied on top of the ground may not help. And that means you can’t pick your cotton.”

In 2007, Culpepper identified the resistant weed in eight more counties, bringing the total number to 18 in Georgia. He estimates that “within a year or two, it will be in the entire state.” He won’t guess at how many acres may be affected in the future, but many observers say it could be 250,000 acres – including soybeans and cotton.

One of the more apparent traps that producers fall into is when they ignore small pigweed outbreaks for two consecutive seasons, and then realize they have a problem in the third year.

“I see that happen a lot, but I think we’re making progress in educating producers,” says the Georgia weed scientist. “Like I said before, they know that prevention is the key.”

Culpepper says he is encouraged at how county agents throughout the state have helped disseminate information to producers.

“Those guys are doing a fantastic job,” he says. “That’s what gives me some hope.”

Contact Tommy Horton at (901) 767-4020 or thorton@onegrower.com.

Working Hard For Solutions To Pigweed Problem

In North Carolina, weed expert Alan York admits that resistant pigweed is serious in several states, but he doesn’t believe the battle has been lost.

“Are we losing the battle?” he asks. “I don’t think so. Actually, I think we’ll be OK. What it boils down to is that we need to work at it a little bit harder. It has the potential to put us out of the cotton business if we don’t get our hands on it pretty good.”

York echoes Stanley Culpepper’s suggestions but says that affected acreage in North Carolina right now stands at about 4 or 5 percent as compared to higher levels in Georgia.

He says it also will pay dividends for producers to go ahead and invest in more chemistry to throw at the problem. He firmly believes in immediately removing the weeds from fields after first spotting them.

Importance Of Pre-Emergents

Other parts of his proactive control strategy involve additional pre-emergent herbicide applications – especially tankmix combinations.

“I’m sure producers may think we’re asking them to mortgage the farm with additional applications,” York says. “But, actually, it’s not that much more than what we’ve been doing.”

Although several options exist for controlling pigweed, York says the best advice is to start the season right with with cleaner fields. Unfortunately, if a producer does not utilize a good tankmix combination of pre-emergents, it’s almost too late to deal with the problem.

“Once the pigweed is out of the ground, there isn’t a lot you can do except eventually bush-hog it,” he says. “If you just cut the pigweed down and leave it in the field, you’re not helping yourself at all.”

In retrospect, York isn’t sure if the approach to the resistant pigweed problem would be any different – even if everyone could turn back the clock 10 years. He would like to think that all parties have learned from their recent experiences.

It all comes down to convincing producers that it pays in the long run to monitor fields and prevent outbreaks before they occur.

“When you go to a grower meeting and tell farmers that they have a one in 10 million chance for some naturally occurring resistance, you can do the math and it comes out to one weed for every 1,000 acres,” says York. “The point is, if you aren’t careful, you might let that one weed run its course in a couple of years. Then, the horse is out of the barn.”

Stewardship Becomes Important

York is convinced that producers know the resistant pigweed is a reality. But he doesn’t believe cotton farmers can get away from glyphosates. For that reason, he is very positive that “proper stewarding of our chemistries can help the situation.”

If that approach doesn’t work, then farmers might be looking at strategies they don’t really want to deal with – such as additional cultivating of crop land.

“I’m still encouraged that we can deal with this problem,” he adds. “Like I said, if we do the smart things, we can win this battle.”

Monsanto Sees Value In Key Partnerships

In an effort to improve the message to producers across the Cotton Belt, Monsanto is working with university researchers to help develop the best recommendations for dealing with the weed resistance problem.

Jennifer Ralston, Monsanto’s Roundup Technical Lead representative, says it is critically important for the company to form a partnership with producers and researchers.

“There is a lot of impact when producers, researchers and suppliers are all on the same page,” she says. “We all have different perspectives but a shared goal of effective on-farm weed management.”

She also says Monsanto is committed to working with weed scientists in publicizing their recommendations to producers.

“The message is clear right now,” she adds. “A producer needs to be proactive in preventing an outbreak of weed resistance. Once you have it, it’s hard to get rid of.”


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