Thursday, April 25, 2024

No surprise — Survey ranks Palmer amaranth as most troublesome weed

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Vicky Boyd
Vicky Boyd

You undoubtedly have seen headlines, such as “10 worst cities in which to live” or “Top 10 worst cities for car theft,” in the popular press or online. The Weed Science Society of America has its own survey in which being No. 1 is a notorious honor.

And it should come as no surprise that Palmer amaranth was ranked the most troublesome weed in 2015 across 26 different cropping systems in the United States. After all, this member of the pigweed family reproduces faster than rabbits, taking over fields in just a few years. It also has become resistant to many of today’s common herbicides.

Coming in as the most common weed was foxtail. Three weeds — common lambsquarter, morningglory species and Palmer amaranth — were in the top five of both the most troublesome and most common weeds.

WSSA defines common as “those weeds you most frequently see,” whereas troublesome weeds are “those that are most difficult to control but may not be widespread.”

Participants in the survey included university and Extension personnel, crop consultants and scouts, industry and government representatives, and land or water managers.

What is a bit odd, until you consider the survey covered all of the United States and not just the South, is marestail was ranked the most troublesome weed and foxtail the most common weed in soybeans.

When you delve deeper and look at the state-by-state data, Palmer amaranth is definitely one of the more common weeds in Southern and Mid-South soybean states. But it may not be the tops.

In Louisiana, for example, participants listed Italian ryegrass and barnyard grass as the most common weeds in soybeans.

Palmer pigweed
Photo courtesy University of Georgia

But look at the most troublesome weed, and Palmer amaranth is either the top offender or one of top two offenders in every Southern and Mid-South soybean state.

The 2015 survey of 26 different crops, non-crop, aquatic and natural areas established a baseline of weed species that will help researchers in the future gauge shifts in populations and management practices, says Lee Van Wychen, science policy director for national and regional weed science societies. “When you look at the Southern Weed Science Society, Palmer amaranth wasn’t even on their radar screen when they started out in the 1970s. It slowly started to grow over the decades.”

WSSA plans to rotate the weed survey every three years, focusing on a portion of the cropping systems annually to avoid overwhelming participants. This year, it is seeking input for weeds of fruits, vegetables, and broadleaf crops including soybeans. In 2017, the survey will focus on weeds in grass crops, pastures and turf. And in 2018, the survey will examine weeds in aquatic systems, non-crop and natural areas.

You can view the complete survey results on the WSSA’s website,

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