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• North Carolina State Weed Scientist Wes Everman says a good first step for farmers in dealing with Palmer pigweed is to be able to accurately identify it at the seedling stage and to differentiate it from smooth and redroot pigweed species.
PIGWEED NUMBERS after grain and cotton harvest can cause big problems for next year’s crop.
Control not economically sustainable
“One hundred percent of all growers who have had success will tell you the same thing,” Culpepper says,
“I was successful in managing the plant, but I’m not economically sustainable. We’re spending $80, $90, $100 per acre to manage this one plant. We cannot keep doing that.”
Everman says, Palmer pigweed with resistance to glyphosate and active ingredients in other often-used herbicides can be a huge problem throughout most of the calendar year.
Growers unintentionally, but routinely, move Palmer pigweed seed around their farm and to neighboring farms on equipment, even on clothing.
Resistance can move considerable distances on pollen. And, it too can be moved via equipment and other means.
Not only are pigweed seed mobile, plants at all stages of growth are also tremendously resilient, the North Carolina State researcher says.
“It’s very common to see Palmer pigweed get knocked down in the harvesting process with corn or soybeans and the farmer thinks the problem is solved. In many cases, I’ve seen pigweed re-root, take-off quickly and be a big problem,” he adds.
“Even mowing doesn’t always have much effect on pigweed. In some cases, mowing may actually mask a later problem with Palmer amaranth.
“Once mowed, these weeds can become a low growing bush, sit there for a while after grain crops are harvested, then come back out before the first frost and be a major problem the next spring,” Everman says.
Whether Palmer pigweed turn up after summer crops are harvested or during the growing season, the surest way to prevent transfer of seed is to pull the weeds up and destroy them.
Labor aside, another problem with that strategy is being able to identify Palmer pigweed when it’s in the seedling stage.
Everman says there are three good, but not easy ways, to distinguish Palmer amaranth from its less destructive cousins redroot and smooth pigweed.
First, look for tiny hairs along the stem of the weed. These fuzzy little hairs are good indicator that the pigweed you have is NOT Palmer pigweed.
Though the names, especially smooth pigweed indicate differences, these pigweed species do have hairs along the stem of the plant and Palmer amaranth does not.