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Preemergence herbicide use grows in 2012

Reminiscing about the good old days in farming conjures up visions of 4-H calves, outdoor hog roasts, and freshly mowed hay.

Then again, not everything was good way back when. Remember creeping jenny? This perennial, also known as field bindweed, was a scourge in fields when Larry Klumb of Ethan, South Dakota, was growing up.

“When we cultivated, we would have to stop the tractor after we hit the creeping jenny patch and clean off the jenny,” says Klumb, who farms with sons Shannon and Ben. “The cultivator would be just like a dump rake. Those jenny patches would just kill us. Every drop of moisture we had would go to the weeds. The corn crop never had full yield potential because there was so much weed pressure.”

As years passed, control of tough weeds like creeping jenny became easier. Preemergence herbicides like Treflan (triflurilan) helped some. Roundup Ready technology with postemergence applications of Roundup (glyphosate) in the mid-1990s greatly enhanced weed control. Still, the Klumbs continue to use preemergence herbicides as a means to set up a later postemergence application and to diversify their weed strategy.

On soybeans, they apply trifluralin or Valor before applying a postemergence Roundup application. On corn, they apply BalancePro preemergence and follow up with Roundup, if needed.

“There's nothing that makes us more money than preemergence chemical,” says Shannon Klumb. “We wouldn't dream of planting an acre without a preemergence herbicide.”

Today, preemergence herbicides are having a renaissance. “Back in 1985, 100% of soy acres were treated with soil-applied product, and just 16% received a post product,” says Bob Hartzler, Iowa State University Extension weed specialist. “Following the introduction of Roundup Ready soybeans, those numbers flipped.”

Advantages of preemergence herbicides include elimination of weed competition early in the season, says Joe Reed, technical field manager for FMC. “A key point is that by controlling earlier emerging weeds, you have greater yield potential,” he adds.

By adding another mode of action, preemergence herbicides also help forestall weed resistance to other action modes. These – and steps like varying application times and even cultivation in severe weed infestations – will be what it takes to forestall herbicide resistance.

These steps are needed because, although there are a few products coming to market, you shouldn't solely depend on them to manage problems like herbicide-resistant weeds.

“In truth, it is nothing like we had in the past,” says Mike Owen, Iowa State University Extension weed specialist. “But in using these products and other changes, there are opportunities to better manage these issues.”

Pyroxasulfone

One new option starting this year in several products revolves around the compound pyroxasulfone, pending regulatory approval.Pyroxasulfone has a growth inhibitor mode of action like acetechlor (Harness, Degree, TopNotch) and S-metalachlor (Dual II Magnum). Three companies will include pyroxasulfone in their products.

● FMC will include pyroxasulfone and fluthiacet-methyl, the active ingredient in FMC's Cadet, in Anthem herbicide. Anthem ATZ herbicides contain these two active ingredients along with atrazine. Anthem can be applied preplant, preemergence, or early postemergence to corn and soybeans. Since it contains atrazine, Anthem ATZ can be applied at these three times to just corn. Company officials expect federal regulators to approve it for corn in late 2012 and for soybeans in 2013.

● Valent plans to launch Fierce, which combines pyroxasulfone with flumioxazin, the active ingredient in Valent's Valor herbicide. It will be a preemergence herbicide for use in soybeans and corn under no-till and reduced tillage. Company officials anticpate approval for uses in corn for the 2012 growing season and in soybeans for the 2013 growing season.

● BASF aims to sell pyroxasulfone in a standalone formulation called Zidua. Federal registration is expected this spring for corn, with registration pending for soybeans and wheat in 2013. Due to timing, BASF plans to commercially introduce Zidua in fall 2012 as a herbicide option to control winter weeds and to provide residual control on fall-germinating palmer amaranth.

Kevin Bradley, University of Missouri Extension weed specialist, notes that mixes containing pyroxasulfone work well to control grasses and small-seeded broadleaves, but it's not the cure-all. He says farmers will need to apply it before even a hint of waterhemp or palmer amaranth surfaces for it to be effective.

Vida herbicide

Vida's active ingredient pyraflufen-ethyl is a PPO inhibitor that can be applied to soybeans and corn as a burndown preplant, at planting, and after planting but prior to crop emergence. It controls numerous broadleaf weeds.

This Gowan product is also a registered postemergence on field corn, popcorn, seed corn, corn silage, and corn stover. Its weed target is for those smaller than 4 inches high.Care must be taken for postemergence applications, though, as crop injury is a concern.

“It needs more precise and accurate application than what typically occurs for corn,” says Owen. “Use it selectively on a field-by-field basis.

Since it's a PPO inhibitor, it also won't work on areas plagued by PPO-resistant waterhemp.

“There are those PPO-resistant pockets where farmers have produced conventional soybeans and have used a lot of PPO-inhibitor herbicides like Cobra,” says Owen.

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