Know Nebraska’s ‘noxious 11’

Warm weather and summer storms aren’t just favorable for growing corn. Weeds flourish as well in this state. Although Nebraska has 11 designated noxious weeds, landowners have a variety of resources that they can use to distinguish friend from foe.

Mitch Coffin, the noxious weed program manager with the Nebraska Department of Agriculture, credits various programs with helping Nebraska’s noxious weed-infested acres shrink from 4 million to 2 million in the past 20 years. “That’s a 50% decrease in infested acres, which I think is huge,” he says.

Concentrated efforts to educate the public about noxious weeds have helped control their populations, according to Coffin.The department administers the state noxious weed program. There are 11 weeds designated as noxious in Nebraska.

“We now have a coordinated program at the county level, a number of new herbicides that have made control a lot better and better education at the landowner level,” Coffin explains.

Manual, chemical, cultural and biological solutions have been implemented to control weed numbers. While this year’s high water levels have caused widespread destruction across parts of the state, Coffin says that the high water does help with weed control in waterways, particularly in controlling phragmites along and in the Platte River.

Noxious weeds, like phragmites and saltcedar, have impeded flows in rivers, especially the Republican River, but Coffin says he doesn’t believe that those weeds have been responsible for consuming large amounts of water. The University of Nebraska has ongoing research assessing the impacts of those weeds on water consumption.

While the battle against noxious weeds rages on every year, Coffin is optimistic that the future of weed control will be more effective and cohesive than in the past.

“When I worked during the Nebraska State Fair 25 years ago, people came in to complain,” he says. “Now, they come to our booth and want to know what’s the next weed on the radar; people want more information.”

More information on each species of noxious weed in Nebraska is provided on these two pages. For more detailed advice on controlling noxious weeds, visit www.agr.ne.gov. All infestation acres are from 2010 data.

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Spotted and diffuse knapweed

There are currently 5,240 acres infested with knapweed in Nebraska.“Knapweed is an example of when we really got ahead of something early,” Coffin says. Knapweed is the newest addition to the list of noxious weeds. Adding weeds to the list has become a better-regulated process in recent years, he adds. “We’re using more science, including a risk assessment program created by the USDA. It asks you questions about a plant: yes, it has potential as an noxious weed, or no, it doesn’t.”

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Canada thistle

The Canada thistle was the first plant to receive noxious weed status in Nebraska, gaining that designation in 1873. Unlike musk and plumeless thistles, which are biennials, Canada thistle is a perennial, making control difficult. Canada thistles are found in irrigated and dryland crop ground, waste areas and roadsides. The weed does extremely well in the flood plains of lakes and reservoirs.

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Leafy spurge

Leafy spurge infests 237,918 acres in Nebraska. Pastures and rangelands tend to have the largest infestations. Cattle and horses will not feed on leafy spurge due to its toxic nature, but goats and sheep will.

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Musk thistle

Musk thistle continues to infest the most acres across the state — 788,461 infested acres. It is a prolific seed producer and those seeds can and will germinate under less-than-ideal conditions, but a number of new herbicides have been developed that have increased the amount of control. Coffin notes that musk thistle infestations make good neighbors into bad ones.

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Plumeless thistle

Plumeless thistle, which infests 60,235 acres in Nebraska, is harder to control than musk thistle, and herbicide rates need to be adjusted to improve control. Since it is a cousin to musk thistle, this plant often has been misidentified. Using natural enemies to combat the thistle is a slow process, but herbicide treatment has proved effective.

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Phragmites

“Phragmites was the biggest noxious weed problem in Nebraska, but because of funding from the Legislature in 2007, it has been better controlled,” Coffin says. The most serious infestations of phragmites are found primarily in the Platte River basin, but the Republican River basin has isolated infestations as well. “Phragmites is probably one we waited too long to designate as noxious,” Coffin says. “It is hard to tell between native and introduced types.”

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Purple Loosestrife

Purple loosestrife was first recognized as a problem in 1992; by the time it was designated in 2001, its numbers had doubled. Purple flowers make it a popular ornamental. It is a wetland invader and infests 6,716 acres in Nebraska.

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Saltcedar

Saltcedar currently infests a little over 5,000 acres in Nebraska, a 58.9% decrease from 2005. “We got on this one off-guard,” Coffin says. Saltcedar invaded exposed lakebeds in Lake McConaughy, Harlan County Reservoir and Swanson Reservoir, but concentrated efforts have saved the lakes from complete infestation.

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Japanese (top) and giant knotweed

These two knotweed species were just added to the Nebraska noxious weed list. They only infest about 5 to 10 acres so far, according to Coffin, and are found mostly in Omaha and Lincoln. They had been planted for erosion control along waterways and drainages. The weeds are difficult to control. NDA, Coffin says, made the designation so that it can be proactive and get ahead of the problem weed.


This article published in the September, 2011 edition of NEBRASKA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2011.