NDSU Extension Service Warns Landowners About Invasive Weed

Oct 28, 2016

Learning to identify Palmer amaranth is the first step to controlling it.

The North Dakota Department of Agriculture and North Dakota State University Extension Service advise farmers to scout new conservation plantings for Palmer amaranth, a very aggressive weed that has plagued cropland production in the South and Midwest.

Palmer amaranth is a type of pigweed that has devastated crops in many states. In some areas, herbicide costs have more than doubled, while producers have not obtained complete control of the weed.

In Iowa, Minnesota and other states, Palmer amaranth recently has been found in many counties where native seed mixes used for pollinator or wildlife habitats inadvertently contained Palmer amaranth seed.

In Georgia, most cotton acres have to be hand-weeded because the weed no longer can be controlled with glyphosate.

“Landowners are encouraged to check their fields and contact the North Dakota Department of Agriculture or NDSU Extension Service if a plant is suspected to be Palmer amaranth,” says Brian Jenks, North Central Research Extension Center weed scientist. “The plant should be growing and identifiable prior to hard frosts.”

Palmer amaranth has several unique characteristics that make it hard to control. In optimum conditions, Palmer amaranth has a rapid growth rate, and can grow 2 to 3 inches per day and reach 6 to 8 feet tall. One plant can produce up to 1 million seeds.

While most weeds have a short emergence window in the spring, Palmer amaranth can emerge throughout the growing season. One of the most troubling characteristics is that it is very prone to developing resistance to herbicides. Some populations are known to be resistant to at least five different herbicide modes of action.

Palmer amaranth’s distinguishing characteristics are:

It has very little hair on the leaves and stem, compared with redroot pigweed.
The petioles are typically as long or longer than the leaf blade.
It is dioecious, meaning it has separate male and female plants.
The female plants have spiny bracts at the leaf axils.
Flowering heads are unbranched and 1 to 2 feet long.
The heads of the female plant are sharp (spiny) to the touch, while the males heads are soft.

Given the history of Palmer amaranth in other states, learning to identify it so that new infestations can be controlled is important for farmers and agronomists, Jenks says.

“This weed is a game changer and will be controlled only by a zero-tolerance policy,” he adds. “Landowners should confirm that any purchased seed does not contain Palmer amaranth.”

Source: ndsu.edu

Video: Spring 2026 weather outlook for Wisconsin; What an early-arriving El Niño could mean

Northeast Wisconsin is a small corner of the world, but our weather is still affected by what happens across the globe.

That includes in the equatorial Pacific, where changes between El Niño and La Niña play a role in the weather here -- and boy, have there been some abrupt changes as of late.

El Niño and La Niña are the two phases of what is collectively known as the El Niño Southern Oscillation, or ENSO for short. These are the swings back and forth from unusually warm to unusually cold sea surface temperatures in the Pacific Ocean along the equator.

Since this past September, we have been in a weak La Niña, which means water temperatures near the Eastern Pacific equator have been cooler than usual. That's where we're at right now.

Even last fall, the long-term outlook suggested a return to neutral conditions by spring and potentially El Niño conditions by summer.

But there are some signs this may be happening faster than usual, which could accelerate the onset of El Niño.

Over the last few weeks, unusually strong bursts of westerly winds farther west in the Pacific -- where sea surface temperatures are warmer than average -- have been observed. There is a chance that this could accelerate the warming of those eastern Pacific waters and potentially push us into El Niño sooner than usual.

If we do enter El Nino by spring -- which we'll define as the period of March, April and May -- there are some long-term correlations with our weather here in Northeast Wisconsin.

Looking at a map of anomalously warm weather, most of the upper Great Lakes doesn't show a strong correlation, but in general, the northern tiers of the United States do tend to lean to that direction.

The stronger correlation is with precipitation. El Niño conditions in spring have historically come with a higher risk of very dry weather over that time frame, so this will definitely be a transition we'll have to watch closely as we move out of winter.