Zero Tolerance Weed Control of Waterhemp/Palmer Amaranth

Growers may remember the first time they saw it staring back at them. Maybe the dirt was still black and the corn hadn’t emerged yet. It was a weed – or weeds – that they hadn’t seen before: waterhemp or Palmer amaranth, also known as Palmer pigweed or simply pigweed.

Growers across the country are taking notice that weeds once dominant in their fields haven’t disappeared, but the likes of waterhemp and Palmer amaranth seem to be taking over. The number of factors that could play into the spread and management of these weeds might seem overwhelming. But growers can turn the odds in their favor with one philosophy: zero tolerance.

That one simple philosophy means growers' odds against waterhemp and Palmer amaranth aren’t as daunting as they seem. With proper management, growers can keep these weeds under control.

Challenging Weeds

Waterhemp and Palmer amaranth are two of the most commonly discussed weeds when it comes to weed shifts and resistance because they reproduce rapidly and prolifically.

"These are two very aggressive weed species in terms of growth habitat and seed production,” said Mark Waddington, product development manager for Bayer. “If left alone and untreated, a single Palmer amaranth plant can produce up to a million seeds. That single weed can be responsible for generations of weeds in the same growing season."

The plants germinate from early spring all the way through the first killing frost. That long window means no chemistry will last long enough to control the entire season of flushes of waterhemp and Palmer amaranth.

"You really need to use multiple products with multiple sites of action and rely on multiple herbicide application timings,” Waddington said. “You can’t let those weeds get big enough to reproduce."

Cultural Controls

Not only are herbicide choices one way to manage tough-to-control weeds, but stewardship and tillage practices come into play too.

"Even equipment use and practices can contribute to the spread of weeds and weed shifts,” Waddington said. “For example, people can run the combine through one field in which waterhemp or Palmer amaranth were present during the season. The seeds are still in the soil that clings to the combine tires, and might transfer to the next field.

"That next field may not have had waterhemp or Palmer amaranth previously, but one or both will likely show up in those fields the next year.”

Bayer Solutions for Growers

The following herbicides are available to help growers beat these tough weeds:

Balance Flexx and Corvus are Restricted Use Pesticides. For more information about waterhemp, Palmer amaranth and their management, visit, call 1-866-99-BAYER (1-866-992-21937) or talk with your local sales representative.

Read More About Managing Weeds

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