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More efficient weed control needed in peanuts

"Peanut producers want and need cheaper weed control strategies," says Eric Protsko, University of Georgia Extension weed scientist. "We have to figure a way to manage our weeds with lower inputs."

About 34 percent of a peanut grower’s production cost is made up of agricultural chemicals, he says. And, while the majority of these costs come from fungicides, herbicides also play a major role, he adds.

"We’ve been asked by growers and by county Extension agents to start looking at weed control systems in the $25 to $30-per-acre cost range. In some cases, we’ve made it to that $30 range, but these cheaper systems won’t work for every grower and in every situation," says Protsko.

Compared to U.S. corn and soybean production, peanuts are considered a minor crop, he says. Nevertheless, several new peanut herbicides have been released in recent years.

"Cadre was released in 1996, and Select was released in 1998," he says. "These were followed by Strongarm in 2000 and Valor in 2001. That’s pretty good for a relatively minor crop. Twenty-two percent or our total peanut herbicides have come on the market in this most recent run, but this run won’t continue.

"There’s not much on the horizon or in the pipeline in terms of new products. The pipeline is drying up, and we’re not looking at any experimental compounds for controlling weeds in peanuts."

The only two "possibilities," says Protsko, are Spartan — a tobacco and soybean herbicide — and Cobra, which is used on cotton and soybeans. "We’re not sure if they’ll make it out of the pipeline. And, if they do, we’re not sure how we’ll be able to use them. There’s just not much out there," he says.

There currently are 18 active ingredients for controlling weeds in peanuts, says Protsko. "That’s quite a few for one crop. Basically, we’ll need to make do with what we’ve got. We might do some things differently with this current arsenal."

The biggest thing peanut growers can do to control weeds and hold down costs is to be more timely in their postemergence herbicide treatments, he says.

"The Number One problem we see in farmers’ fields is that weeds are too big when they are sprayed. Please try to get out earlier with your weed control strategies, particularly when making postemergence treatments."

It’s also important, says Protsko, that growers pay more attention to details. "We need to know more about our weed problems — things such as the biology of the weed and competition. Knowing these details will help us to make better decisions. We need to match our weed program to the specific weed problem."

With 18 active ingredients, the tools are available for growers to do a good job of controlling weeds in peanuts, he says. "We just have to figure out how to do it with a $355-per-ton peanut."

Researchers are looking at several ways of reducing peanut herbicide costs, says Protsko. "We’re looking at new uses for old products. Is there a combination of these products or materials that might give us some benefit? Strongarm came along a few years ago as an excellent soil-applied material. Now, it’s available for PPI use, pre-emergence for broadleaf weed control.

"We’re also looking at it for postemergence treatments because we noticed some postemergence activity. Hopefully, we’ll be able to come up with some uses that’ll result in savings."

Herbicide combinations is another possibility for reducing costs, he says. "Many growers are using both Strongarm and Valor in their weed control programs. We’ve been looking at the combination of these two materials, and they complement one another very well. Used together, they probably will control a wider spectrum of weeds than if they are used individually. And, since these two materials have different modes of action, we might be reducing the risk of forming resistance by using them in combination."

The label doesn’t currently allow for Strongarm and Valor to be tank-mixed, says Protsko. "There are good reasons for that. But hopefully, we can work through these issues."

Many growers also have reduced the rates of herbicides to cut input costs, he says. "One of the first things you think about when lowering input costs is to cut herbicide rates. But it’s not that simple. Many factors contribute to the success of a herbicide application — you can’t just cut the rate. There must be a better understanding of what’s occurring in the field.

"We know it’s already being done. Growers seem to be using Cadre at a lower-than-recommended rate. We had a 50-percent price reduction in Cadre last year, but that didn’t stop growers from lowering the rate. It might have made matters worse because some fields were sprayed two times with Cadre."

Peanut weeds can be controlled at lower-than-recommended rates in certain situations and under certain conditions, notes Protsko. The labeled rate, he adds, is designed to give farmers the best control over a wide range of conditions.

"But there are situations where we know what’s going on in the field, and we can do a good job with reduced rates. But I don’t think reduced rates is the answer to our cotton problem with Cadre. Our research has shown varying degrees of injury from different rates of Cadre. That’s just not a good reason to cut the rate of Cadre."

In looking at programs for reducing peanut herbicide costs, Protsko describes one that uses Sonalan or Prowl as a preplant incorporated, pre-emergence treatment. This is followed by Boa or Gramoxone Max at cracking and Cadre at postemergence, with a 1-ounce rate of Cadre. The cost of this program, he says, is about $20.

"Of course, there might be weeds that come through. I’d keep 2, 4-DB as an option, at only a couple of dollars per acre.

Another program uses Sonalan pre-emergence, tank-mixed with Valor, and followed by Cadre. The cost of this program would be about $32 per acre.

"We’re using Cadre in each of these programs, and that might be a problem for some growers due to rotational restrictions. But the price reduction of Cadre has made it a good option."

Another program, says Protsko, would be similar to the first one but would add Storm with the at-cracking spray, bringing the cost to about $32 per acre.

Researchers also looked at a program consisting of Pentamax pre-emergence plus a Strongarm pre-emergence followed by Cadre. This program would cost about $35.16.

"Following Strongarm with Cadre probably isn’t such a great thing to do in terms of resistance management, but it’s being done based on growers’ individual needs." e-mail:

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