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Late-Season Herbicide Applications May Be Ineffective

Kacey Birchmier 08/04/2014 @ 3:44pm I grew up on a fourth-generation farm in central Iowa. Follow me on twitter - @KaceyBirchmier.

If you have weeds growing in your fields at this point in the growing season, herbicide applications may not be your best option.

"The majority of weeds in corn and soybean fields are much higher than the ideal 4- to 8-inch height, and herbicide applications are only going to provide marginal control at best," says Travis Legleiter, Purdue Extension weed scientist.

Because weeds are past the ideal height for herbicide applications, hand-rouging and pulling by hand may be the best way to remove weeds.

The most common weeds that may not be under control at this time in the season are Palmer amaranth, common waterhemp, giant ragweed, and marestail. If herbicides are repeatedly applied to these larger, full-grown weeds, the offspring are more likely to be herbicide-resistant, Legleiter said.

"Although it is human instinct to try and spray something and do something about the tall, ugly weeds in our fields, we may be better off not spraying and not selecting for resistant biotypes," said Legleiter.

Beware of carryover
Another risk that comes with spraying herbicides late with residual activity specifically is the possibility of the herbicide carrying over into the winter and spring, which can be potentially damaging to those crops.

"Hand-rouging and hand-pulling may be our only options at this point and the most effective, even though it will be the most time- and labor-intensive option," Legleiter says.


Source: Ag Answers

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you have got to be kidding me 08/05/2014 @ 12:39am You can't spray herbicides this late in the season in North America if you want a salable crop.

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