New weed control technologies offer advantages

An Alabama Cooperative Extension System weed scientist believes two new weed control technologies merit a closer look by cotton producers.

One of the new technologies, Syngenta's Envoke, is a conventional herbicide that can be applied at extremely low rates.

“It's not a genetically engineered product like Roundup Ready or Liberty Link but a true chemical-discovery herbicide that can be used at only one-tenth of an ounce per acre. That's roughly a teaspoon of material per acre,” says Mike Patterson, an Alabama Cooperative Extension System weed scientist.

Patterson presented his findings on new weed control technologies at the Alabama Cotton Field Day, held recently at the Tennessee Valley Research and Extension Center in Belle Mina.

A foliar-applied herbicide, Envoke also has some residual activity. It is effective on morningglory, sicklepod, pigweed and several other weeds.

“I've seen it kill good-sized morningglory and sicklepod between 6 and 8 inches high,” Patterson observed. “It also has significant nutsedge activity.”

Envoke can be sprayed over-the-top of both conventional and transgenic crops. On the other hand, one limitation associated with Envoke is that the chemical can be applied only after the cotton has reached the fifth true leaf.

“You can't go early with it, which is a bit of a disappointment,” he stressed. “That means if you're growing a conventional variety, you're going to have to use some other product to get your product to the fifth leaf stage before you can use Envoke.”

Liberty Link cotton is another technology Patterson believes shows great promise.

Like its competitor, Roundup Ready cotton, Liberty Link is a genetic technology that will require growers to buy Liberty Link cotton in order to use the herbicide product.

“Liberty Link (herbicide) kills both Roundup Ready and conventional cotton, so growers who use it should make sure it is applied only to Liberty Link cotton, just as Roundup should be used only with Roundup Ready cotton.”

As a postemergence herbicide, Liberty Link is similar to Roundup. It is a broad-spectrum product that kills broadleaves as well as grasses.

“It may even work a little bit faster than Roundup,” Patterson says. “One added advantage is that Liberty Link cotton may have more tolerance at a later stage to herbicide applications.

“Roundup Ready, as most growers know, is limited to the fifth leaf stage. After that, you can't spray over-the-top without risking a yield reduction. Liberty Link, on the other hand, is tolerant up to the bloom stage — a valuable tool if you are dealing with escaped weeds.”

One added advantage associated with Liberty Link is that it appears to be stronger on morningglory, though it appears to be weak on large annual grasses and pigweed.

Liberty may also help some producers obtain better control of herbicide-resistant weeds, especially in north Alabama's Tennessee Valley where growers are dealing with Roundup-resistant horseweed.

Bayer, the product manufacturer, also hopes to be granted a label permitting its use in burndown prior to no-till planting, Patterson says.

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