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Posted 27 April 2015. PMN Crop News.

Fight Weeds Through Scouting and Herbicide Application Timing, Says Clemson Researcher

Source: United Soybean Board Press Release.

Chesterfield, Missouri (April 15, 2015)--Herbicide-resistant weeds, such as Palmer amaranth, are a known threat to South Carolina soybeans. These weeds can spread quickly, reduce land values and threaten soybean yields if not effectively managed.


While most farmers are aware of the problem, increased management is needed to control weeds, according to Mike Marshall, Ph.D., extension weed specialist at Clemson University.

“The level of management is not where I would like to see it,” says Marshall. “I would like to see farmers spend more of their resources and time on soybeans. In the past, weed problems got out of hand because the necessary level of management was not there.”

As farmers get in the fields this spring, they still have time to create a comprehensive weed-management program in order to avoid weed problems during the growing season.

According to Marshall’s research, the most important aspect of any weed-management plan is when you apply your herbicides.

“It all boils down to timing,” says Marshall. “If you wait a week to ten days to spray emerged weeds, your expected control can drop off significantly, especially with Palmer amaranth.”

Palmer amaranth can take control of a field in a matter of days because of its ability to produce up to 1 million seeds per plant. This means that waiting to address a Palmer amaranth weed problem, even for a few days, could mean the difference between a clean field and one overrun with weeds.

For maximum weed control, Marshall suggests that farmers get out in their fields and scout for weeds on a regular basis.

“It is important that farmers be aware of which weed populations are present in their fields,” Marshall says. “Good scouting practices are a critical step in developing a proactive weed-management plan.”

For more information and resources from the soy checkoff to help you manage herbicide-resistant weeds, visit