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For cotton: New weed control technology coming

For those cotton producers who have witnessed unprecedented weed control problems this year, help is on the way. Several new cotton herbicide technologies are in the pipeline, with commercialization expected in the very near future, says Mike Patterson, Auburn University Extension weed scientist.

“Cotton producers will see new technologies — hopefully within the next two years — that will be improved tools for producing cotton and for controlling weeds in cotton,” said Patterson at a central Alabama cotton field day.

One of these new technologies is the Liberty Link system from Aventis, he says. “Liberty Link is a herbicide that's very similar to Roundup in the way that it kills weeds. It's a broad-spectrum, postemergence, over-the-top herbicide that kills both broadleaf weeds and grass,” says Patterson.

The Liberty Link system is a genetic technology, he explains, meaning that the herbicide will kill non-transformed cotton.

“A gene has been placed into Liberty Link cotton just as in Roundup Ready varieties. This gives the cotton tolerance to Liberty herbicide. Liberty is glufosinate while Roundup is glyphosate, so you can tell by their common names that they're somewhat similar in their chemistry.

“When this technology is commercialized, hopefully in the year 2003, you'll be able to use Liberty on Liberty Link cotton in a similar fashion that you now use Roundup on Roundup Ready cotton. There are, however, a couple of differences in the two systems,” says Patterson.

Application timing

One of these differences, he continues, is the tolerance of Liberty Link cotton to over-the-top applications of Liberty herbicide. Liberty Link cotton currently has tolerance up to the bloom stage, notes Patterson.

“Aventis anticipates it will have this gene in one of their high-yielding, high-quality FiberMax varieties in 2003. It will have more vegetative tolerance to Liberty than we have in the current Roundup Ready varieties, where we have to stop over-the-top applications at the fifth leaf stage.”

Patterson also believes Liberty will work quicker than the current Roundup Ready systems. “You'll probably see a more rapid weed kill with this new Liberty technology.”

Another new technology, with commercialization expected in 2004 or 2005, is a new generation of Roundup Ready cotton, says the weed scientist.

“We're looking at this new generation in north Alabama, and they're hoping it will have tolerance up to the eight to 10-leaf stage. It might even be more tolerant than that. This new generation currently is being evaluated at research stations throughout the country. We're probably four to five years away from having this new generation gene placed in varieties that you'll want to grow on your farm.”

A third new technology is the herbicide Valor, says Patterson. “We've tested Valor in central Alabama and at other research stations in the state for the past three years. It's a relatively low-rate, postemergence, directed herbicide that probably will be a good replacement for Bladex, if it gets a label for cotton.

“It's a hot material, so you'd have to keep it down and direct it low on the cotton stalks. Valor received a registration for peanuts this past spring, where it's used as a pre-emergence treatment. It has some soil residual activity. But it does not, in my opinion, have so much residual activity that it'll prevent you from rotating to small grains if you're in a no-till situation.”

Valor, he says, has activity on broadleaf weeds and grasses. “Just remember that Valor is a hot, contact material, so you'll need to make directed treatments on the woody part of the stalk. You'll use it just as you would use Bladex. It could receive a label for cotton within a year or so.”

Another herbicide product currently in university trials is Brawn from Syngenta, says Patterson. Brawn is a traditional herbicide, he says, in that it was developed by a chemist working in a laboratory.

“Brawn is unique because it's an extremely low-rate product when used on cotton. It probably will be registered for over-the-top broadleaf weed control in cotton. It controls a wide range of broadleaf weeds, and it also has some nutsedge activity. You won't get grass control with Brawn, so you'll have to use another material with it.

“The advantage of a product like Brawn is that it isn't linked to a gene. In other words, you can spray it on conventional, Roundup Ready or Liberty Link cotton varieties. The use rate is very low. For example, Staple, which we have used for several years, is used at 1.2 ounces of product per acre. Brawn will be used at about one-tenth that rate. This product should be ready for use in 2003.”

New defoliants

Several new cotton defoliant products are available to producers this year, says Patterson. LeafLess — from Uniroyal — is a combination of Harvade and Dropp in a liquid form, he says.

“They recommend that you use a crop oil concentrate with this product. We looked at it in trials last year, and it did a good job of defoliation. The Dropp in this formulation will provide you with some regrowth suppression. If you want to open a boll with it, you can add an ethephon material such as Prep, Finish, or CottonQuik.”

Another new harvest aide product for 2001 is Aim from FMC. “Aim basically is a herbicide. It received registration as a post-directed herbicide in cotton and also as a harvest aide. This is another low-rate product, with a use rate of two thirds to one ounce per acre. The label classifies the product as a defoliant and desiccant. If you go with the one ounce rate in hot conditions, you may stick some leaves.

“Aim is a very fast-acting, contact material. It is recommended that you use a crop oil concentrate with that two thirds ounce, about one gallon of crop oil concentrate per 100 gallons of spray solution. Aim will give you defoliation, but it won't open a boll or suppress regrowth. You'll probably want to use Aim with one of the ethephon materials. Aim alone probably won't do the job on cotton defoliation unless you make a sequential application.”

Another new product — FreeFall — is a form of Dropp from Griffin, says Patterson.


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