Farmers and land managers planting conservation seed mixes should be on the lookout for an aggressively invasive weed called Palmer amaranth, state plant protection officials say. In addition, anyone packing and labeling such seeds must take steps to avoid contaminating the mixes with Palmer amaranth.
Under a new emergency rule in Wisconsin, Palmer amaranth is a prohibited noxious weed seed, and including it in a seed mix would be a civil or criminal violation for the seed labeler.
“Once established, Palmer amaranth can out-compete other native plants in conservation plantings, and if it gets into corn and soybeans, can cause yield losses as high as 90 percent,” said Brian Kuhn, director of the Plant Industry Bureau in the Wisconsin Department of Agriculture, Trade and Consumer Protection. “This is an incredibly invasive, incredibly expensive-to-control weed. It’s been highly destructive in some of our neighboring states, and we don’t want to see that in Wisconsin.”
Palmer amaranth is a broadleaf weed that grows 2-3 inches a day. It commonly grows 6-8 feet tall, but may reach 10 feet. It has separate male and female plants, and the females may produce as many as 500,000 seeds. It is related to water hemp and other “pigweeds”, common in Wisconsin, and a casual observer might confuse the two.
Native to the southwestern United States, it has now spread to other areas of the country. In the past, it usually was spread on equipment, in feed or by wildlife, so it didn’t spread very rapidly and could be eradicated in a field fairly easily. It has been found in a handful of sites in Wisconsin where it was brought in by these methods.
But in recent years, it has gotten into seed mixes that farmers plant as pollinator habitat on conservation acreage, such as land in the Conservation Reserve Program. Left to go to seed in these areas, it spread to new areas rapidly. Iowa has had a particularly severe problem, with more than half the counties there now infected with Palmer amaranth. To date, Wisconsin has not found it in conservation plantings.
Kuhn said, “We want to keep it out of Wisconsin as long as possible. Our pest surveyors have been trained in spotting Palmer amaranth, with help from the University of Wisconsin-Madison. We’ve sent information to our licensed seed labelers. And now we need landowners to join the effort.”
Anyone planting a pollinator or conservation seed mix should:
- Be aware of what Palmer amaranth looks like. You can find many clear photos in an online image search.
- Buy local seed mixes if possible, with no pigweed or amaranth listed on the label.
- Thoroughly clean equipment after seeding, especially if your seed mix came from out of state.
- Call your University of Wisconsin-Extension office if you suspect you have found Palmer amaranth.