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Preemergence herbicide use grows in 2012

Gil Gullickson 03/06/2012 @ 9:49am Crops Technology Editor for Successful Farming magazine/Agriculture.com

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.”


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.

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