WSSA Ranks Troublesome Weeds

Kelly MarshallAg Group, Weed control

weed science societyIf you farm within the U.S. it’s probably not a shock to learn that the Weed Science Society of America (WSSA) has ranked Palmer amaranth, or Palmer pigweed, as the most troublesome weed in the country.  Those in Canada reported weeds in the Galium genus (cleavers, catchweed bedstraw and false cleavers) as the most difficult to the north.

“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.”

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. 

Those in the U.S. listed Palmer amaranth, morning glory, lambsquarters, water hemp and horseweed (marestail) as the most troublesome, while most common were reported as foxtail, lambsquarters, crabgrass, Palmer amaranth and morning glory.  In Canada the species found in Alberta, Saskatchewan and Manitoba dominated the list with Galium, wild oat, Canada thistle, kochi a, and while buckwheat found as the most troublesome.  The most commonly reported weeds were wild buckwheat, wild oat, pigweed, foxtails and lambsquarters.

The survey also broke down weed difficulties by ecosystems for both countries as well.  You can see the results of the survey  at, and check thesScientific names in the WSSA composite list of weeds at