The 10 most troublesome weeds in broadleaf crops

After surveying nearly 200 weed scientists across Canada and the U.S., the Weed Science Society of America published its top ten list of “most troublesome” weeds in broadleaf crops this week.

Fortunately, the most troublesome weed has not been found in Canada (yet), but there are certainly some familiar foes on this list. (Maybe there’s some consolation in knowing you’re not alone?)

The 10 “most troublesome” weeds, according to weed experts:

10. nightshade (eastern black, hairy)
9. giant ragweed
8. common ragweed
7. kochia
6. nutsedge (yellow, purple)
5. waterhemp (tall, common)
4. morningglory (ivyleaf, pitted, tall)
3. horseweed (marestail)
2. common lambsquarters

And…no surprise…

1. Palmer amaranth

WSSA published a separate list of “most common” weeds in broadleaf crops, with number one widely distributed across southern Canada and the northern half of the U.S.

Lambsquarters (Photo by Debra Murphy, 2016)

The 10 “most common” weeds:

10. velvetleaf
9. barnyardgrass
8. common ragweed
7. horseweed (marestail)
6. waterhemp (tall, common)
5. redroot pigweed
4. Palmer amaranth
3. morningglory (ivyleaf, pitted, tall)
2. foxtail (giant, green, yellow)
1. common lambsquarters

Palmer amaranth, common lambsquarters, horseweed, morningglory, waterhemp and common ragweed are on both lists. They also have something else in common:

“Weed scientists have confirmed multiple cases of herbicide resistance in all six of these weed species, except for the morningglories, where there is suspected resistance to glyphosate,” notes Lee Van Wychen, science policy director for WSSA. “While each of these species has evolved traits that make them widespread and tough competitors in broadleaf crops like soybeans and cotton, there is no question that their difficulty to control with herbicides has pushed them to the top of the list in this survey.”

Kochia

The survey data was also sorted to show the most troublesome weed and most common weed, respectively, by crop:

alfalfa: Canada thistle; dandelion
canola: kochia; wild oat
cotton: Palmer amaranth; morningglory (ivyleaf, pitted, tall)
fruits & nuts: field bindweed; horseweed (marestail)
peanuts: nutsedge (yellow, purple); Palmer amaranth
pulse crops: common lambsquarters; common lambsquarters
soybeans: horseweed, waterhemp (tall, common); waterhemp (tall, common)
sugar beets: common lambsquarters; common lambsquarters
vegetables: nutsedge (yellow, purple); common lambsquarters

WSSA’s 2017 survey will focus on weeds in corn, cereal grains, pastures and other grass-type crops.

Related: Lambsquarters Tops Farmers’ List as Ontario’s Worst Weed

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