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Don’t Be a Weed Chaser

Forming a weed-management plan prior to the growing season helps farmers get a jump on weeds.

Ever seen those crazy folks who chase tornadoes on TV? It’s fun to watch, and probably even funner to do – if you come out alive, that is. Just don’t transfer that skill to chasing weeds that get ahead of you during the growing season.

Take the time to form a weed-management plan before the season starts, advises Dave Ruen, a Dow AgroSciences field scientist. “This is like financial planning,” he says. Making a weed-management plan at the year’s start with a trusted agronomist or crop adviser can prevent you from chasing weeds that get ahead of you during the growing season.

Ruen and Lindsey Hecht, Dow AgroSciences U.S. soybean herbicides product manager, shared some weed-management ideas at a Dow field day last week near Maxwell in central Iowa.

• Plan on applying a preemergence residual herbicide

“Start with a preemergence residual herbicide at full rates,” says Hecht. Patience is needed, as effectiveness hinges on rainfall for incorporation and soil temperatures. Warmer soil temperatures that occur if planting is delayed increases the need for activating rainfall, as weeds rapidly grow in warm temperatures.

In most cases in the spring, though, rainfall received seven to 10 days after application is sufficient for activation, says Hecht.

Preemergence residual herbicides are especially important when it comes to managing the Satanic weed, Palmer amaranth.

“Never give it an opportunity,” says Ruen. “Start clean and apply a residual (preemergence herbicide) at a full rate. Two things that can sink a weed-control program is no preemergence (residual herbicide) and an untimely post application,” he adds. “You may have to make a second post application too.

• Use different tools

A diversified financial portfolio consists of various investments – stocks, bonds, real estate – to enable investors to ride out bumpy financial times. It’s the same way with weeds. Weed pressure and weed types won’t be the same every year. Weather conditions will vary. “Different weeds emerge at different times,” says Ruen.

Mixing up different modes of action with both preemergence and postemergence herbicides give a broad control spectrum that can help protect farmers against any unexpected turns that weeds may take. A diverse weed-management plan that has helped farmers curb waterhemp also can benefit famers when it comes to Palmer amaranth.

“If you have minded your p’s and q’s for waterhemp, you will be in good shape with Palmer,” says Ruen. “Palmer is not like a monster that can’t be slayed. But it requires a program approach. It needs to be respected, but not feared.”

• Remember cultural practices 

Narrow rows that help soybeans form a canopy quicker can also snuff weeds. They can still slip through the canopy, say Hecht and Ruen, although they will have tiny roots that make them easy to pull. The bad news is that weeds like waterhemp still can be healthy enough to make a seed head, so it’s important to pull them.  

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