COLUMBIA, Missouri (DTN) -- Palmer amaranth is giving validity to the curmudgeon's view that no good deed goes unpunished. Researchers at the University of Missouri are now finding birdseed is often packed with pigweed and many other weed seeds.
The news comes after Palmer amaranth, an aggressive pigweed species that is a scourge in southern states, was found popping up in pollinator plots across the Midwest last year. Missouri scientists have also pointed to waterfowl contributing to the continued spread of the weed as the birds eat and subsequently poop the undigested and still viable pigweed seeds far away from the point of initial consumption.
Until now, physical movement by way of machinery or contaminated livestock feed or bedding has largely been blamed for Palmer making its way northward. But these new avenues of entry give growers additional reasons to keep an eye open for the opportunistic invader, says University of Missouri weed scientist Kevin Bradley.
Bradley's graduate student, Eric Oseland, presented the birdseed findings at the university's recent Integrated Pest Management field day. Palmer amaranth has become the weed to watch in the state as it has spread to 39 of Missouri's 114 counties. Last year some populations of Palmer amaranth were found capable of resisting multiple classes of herbicides.
Oseland buys birdseed at retail outlets and screens the seed for weeds. Palmer amaranth seeds are about the size of a pinhead, so he plants the seeds and lets the weeds emerge to determine what is present in the mix.
He found some type of pigweed (amaranthus) species in almost all birdseed that he has screened to date, although not every brand contained Palmer amaranth. Common ragweed, velvetleaf and morning glory were other weeds there were common in the brands he sampled.
According to Oseland, birdseed mixes that include millet tend to contain the most weed seeds. One brand he screened contained nearly 8,000 pigweed seeds in a single pound bag. That's a lot of pigweed since birdseed often sells in 50 lb. bags.
One female Palmer amaranth plant can produce 1 million seed and remain viable in the soil for years. Controlling the weed seed bank has become an important tactic in reducing the spread of troublesome weeds.
Oseland is also studying pollinator mixes being used for the USDA's Pollinator Habitat Initiative, which is part of the Conservation Reserve Program (CRP). So far, more than 60% of the pollinator mixes he has screened have contained Palmer amaranth seeds.
CRP pollinator plots are typically planted to fast-blooming forage legumes and wildflowers that seed suppliers source from a variety of sources. Iowa, Illinois and Minnesota are some of the states where weed scientists have reported Palmer in pollinator plot problems.
For now, the only way to control Palmer pigweed in pollination plots is hand weeding. Growers are urged to pull weeds while small and to keep in mind that Palmer grows and forms seed heads quickly.
Bradley said their studies have also shown that waterfowl can transport and distribute viable Palmer amaranth seed over long distances. "The initial distribution of Palmer amaranth along the Missouri river bottoms led us to investigate," he noted.
Waterhemp, common lambsquarters, giant foxtail and smartweed were also found to be distributed in this manner.
For more information on waterfowl and Palmer amaranth distribution, you can view a slideshow of the Missouri research results here:
Feeding the birds and the bees remain worthwhile and important to helping keep nature in balance. "However, we are doing this work because we feel it is an issue that we need to be aware of," Bradley told farmers during the Missouri field day. "We need to be scouting and watching for Palmer because it is so aggressive and can quickly gain a foothold."
A good weed guide to help identify Palmer from other pigweed can be found here: http://weedid.missouri.edu/…
Find a guide to controlling Palmer amaranth here: http://weedscience.missouri.edu/…
Pamela Smith can be reached at Pamela.firstname.lastname@example.org
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