Let’s face it. Cotton farmers in the lower Mid-South have other things to do besides spraying corn with a postemergence herbicide. Things like planting cotton, spraying cotton with postemergence herbicides, spraying cotton for thrips and plant bugs….

That’s why Syngenta Crop Protection has developed Lexar, a new pre-emergence herbicide that is designed to deliver one-pass weed control on more corn acres across the central and southern corn-growing regions of the United States.

“We wanted a product that would give us the broadest spectrum weed control, pre-emergence, in corn,” says Doug Anderson, Syngenta crop manager for Southern field crops. “It needed to be wide-reaching– not only from a pre-, but also from an early postemergence standpoint. And it needed to be very consistent.”

Although Mid-South farmers planted more corn when December futures were above $3 per bushel last spring, many would say corn is a rotation crop and cotton commands their attention once the latter goes in the ground.

“Most of you know that this is a Bicep geography,” said Anderson, who spoke at a Syngenta press briefing for Lexar at Syngenta’s Southern Regional Technical Center near Leland, Miss. “Bicep II MAGNUM is the mainstay here in the South.

“One of the things that you hear is that probably 70 to 80 percent of the time Bicep II MAGNUM provides one-pass weed control for most of our growers in the South. We can increase this with Lexar, we believe, because of the Callisto in the product.”

Anderson said some weeds in the South, Johnsongrass and shattercane being two, are a challenge for a one-pass weed control program. “Some of the remaining difficult weeds – cocklebur, sunflower, morningglory – is where Lexar will shine.”

Lexar, which is expected to receive EPA registration this fall, combines mesotrione, the active ingredient in Callisto; S-metolachlor, the active ingredient in Bicep II MAGNUM and Dual II MAGNUM; and atrazine.

It may be applied to corn from 14 days prior to planting to when the corn reaches 12 inches in height but it must be used prior to weed emergence to achieve broad-spectrum control. Lexar was designed to provide residual control of six weeks or longer.

Anderson said researchers have not encountered any of the crop safety problems with Lexar that growers have seen with some competing products. “This product is safe to corn,” he said, “so we’re not buggy-whipping or stunting the corn.”

In tests with a number of grass species, Lexar provided 95 percent control compared with 90 percent control for Bicep II MAGNUM and 93 percent control for LUMAX, Syngenta’s new herbicide that is targeted for the northern reaches of the Corn Belt.

“You would expect Lumax to do well on grasses because it contains 1.7 pints of Dual II Magnum or S-metolachlor,” said Anderson. “But Lexar also performs very well on broadleaf weeds when it is compared to Bicep II MAGNUM and to Lumax.”

After registration is received, Syngenta will position Lexar as a product that should be used as early as possible to prevent early season weed competition in corn.

“It’s generally accepted that corn is more sensitive than soybeans to early season weed competition,” says Mike Johnson, technical brand manager for Syngenta. “In corn, yield loss typically begins when weeds are in that 2-to-4-inch-height window, but exactly when depends on a lot of different things – weed pressure, weed species, soil moisture and fertility.

“Delays in postemergence weed control can cost 2 percent of your yield for each leaf stage of corn that you delay or about 3 to 5 percent per week of delay.”

A number of university studies have shown that weeds that emerge with the crop will be the most competitive. “If you miss an application at planting, you start losing yield right away,” he said. “Conversely, if you start too early with a postemergence treatment, you can get another flush of weeds on into the season.”

“Farmers say that when they harvest, all they want to see corn,” Anderson says. “They don’t want to see scattered pigweed or broadleaf signalgrass out there. When you use a glyphosate system without a pre-emerge, you’re going to have late emerging pigweed, late emerging grasses when the corn starts drying down, which causes problems with harvesting, and you get increased moisture in your corn. Plus, most farmers would like to use corn as a glyphosate resistance management crop.”

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