Between genetically modified soybean varieties and the use of glyphosate and glufosinate, Iowa State University Extension Weed Specialist Mike Owen believes growers may have a false sense of security when it comes to weed control. Owen says many growers believe they can move in to control weeds at any time and postpone the use of herbicide applications. According to Owen, that’s not a good idea. What growers need to do is differentiate between the concept of killing weeds and the concept of managing weeds to have the most yield potential.

“Managing weeds, which is the critical issue, means that the weeds have been removed from the soybean crop in a timely fashion such that the yield potential of the soybeans is not compromised.”

Owen says growers need to get in field earlier than they think.

“We have long been touting the need to apply a pre-emergent, residual herbicide for all crops – corn and soybeans. In many instances, we are suggesting that applying these herbicides as an early preplant treatment, maybe one, two or three weeks ahead of their anticipated planting date, is the best way to achieve the security of early season weed control, which essentially protects the crop yield.”

Owen says the problem is compounded when growers have both corn and soybeans, and in many cases, herbicide treatments were not used on the corn crop, and when the crop came up, so did the weeds. According to Owen, both corn and soybeans respond poorly to early season weed competition. Add in wet weather and growers are faced with the decision to either spray corn or soybeans. This snowball effect, Owen says, will take a toll on yield and profitability. However, there is something growers can do.

“In many instances we are still in a position where we can go out with an early post application to control the emerged weeds and include a residual treatment, which I think will pay dividends in corn, and there are some treatments we can use in soybeans, as well. Don’t forget to consider the residual treatments.”

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