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Palmer amaranth is most troublesome weed in U.S.

Palmer amaranth is most troublesome weed in U.S.

Hundreds of weed scientists, extension agents and practitioners across 49 U.S. states, Puerto Rico and eight Canadian provinces participated in the 2015 Weed Science Society of America survey.

It’s now official. A survey conducted by the Weed Science Society of America has ranked Palmer amaranth, also known as Palmer pigweed, as the most troublesome weed in the U.S.

“We certainly weren’t surprised to find Palmer amaranth at the top of the U.S. list,” says Lee Van Wychen, Ph.D., science policy director for WSSA. “This weed can have a devastating impact on crop yields. Its stems are tough enough to damage rugged farm equipment, and it is extremely prolific. A single Palmer amaranth plant can produce as many as a million seeds during a growing season.”

Related: Palmer amaranth time-lapse videos stress early control

Palmer amaranth is the most troublesome weed in the U.S. (Photo: Joseph M. DiTomaso, University of California-Davis,

Hundreds of weed scientists, extension agents and practitioners across 49 U.S. states, Puerto Rico and eight Canadian provinces participated in the 2015 WSSA survey. They provided input on both the most common weeds (those most frequently seen) and the most troublesome weeds (those most difficult to control) in 26 different cropping systems and natural areas.  The lists below are based on an aggregation of their responses, which mentioned more than 650 weeds at least once.

Most Troublesome Weeds, U.S.

Most Common Weeds, U.S.

1. Palmer amaranth

1. foxtail (giant, green, yellow)

2. morningglory (ivyleaf, pitted, tall, sharppod)

2. common lambsquarters

3. common lambsquarters

3. crabgrass (large, smooth)

4. waterhemp (common, tall)

4. Palmer amaranth

5. horseweed (marestail)

5. morningglory (ivyleaf, pitted, tall, sharppod)

Three weeds – common lambsquarters, morningglory species and Palmer amaranth – appear on both lists above.

Related: Study underscores need for zero-tolerance Palmer amaranth control

Among the other significant findings from the 2015 WSSA survey were the most troublesome and the most common weeds in several key crops and ecosystems across the U.S. and Canada:


Most Troublesome Weed

Most Common Weed

Aquatic systems


watermilfoil (Eurasian, hybrid)

Cereal grains, spring

wild oat

wild oat

Cereal grains, winter

downy brome/cheatgrass

downy brome/cheatgrass


waterhemp (common, tall)

foxtail (giant, green, yellow)


Palmer amaranth

Palmer amaranth

Parks, wildlife refuges

Canada thistle

downy brome/cheatgrass


Japanese stiltgrass (Mary’s-grass, Nepalese browntop)

Japanese stiltgrass (Mary’s-grass, Nepalese browntop)

Fruit and nut crops

eastern poison-ivy

red sorrel

Pastures, rangelands, right of ways

Canada thistle

Canada thistle


horseweed (marestail)

foxtail (giant, green, yellow)


annual bluegrass

crabgrass (large, smooth)


nutsedge (yellow, purple)

common lambsquarters

The 2015 survey data is available at Scientific names for the weeds above are available in the WSSA composite list of weeds at

Related: Prepare to control Palmer amaranth

WSSA plans to conduct its weed survey annually, with a three-year rotation of different weed habitats. The 2016 survey focuses on weeds in broadleaf crops, fruits and vegetables.  The 2017 survey will focus on weeds in grass crops, pastureland and turf, while the 2018 survey will focus on weeds in aquatic environments, natural areas and other noncrop settings.

Source: Weed Science Society of America

TAGS: Soybean
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