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Weed presents a dangerous foe, must-win battle

Weeds have been a problem since crops were first cultivated. Farmers, on the front lines of the age-old battle, know all too well that weeds are a relentless foe. At Agweek, we've committed much of our time and resources reporting on weeds and weed management to improve agronomic practices across our region.

But a new weed, Palmer amaranth, is invading the Upper Midwest region. Most agriculturalists here probably don't fully realize how dangerous and destructive it is — and how little time they have to prepare for its arrival. Because of its threat to our region, we had two cover stories on Palmer amaranth over the past few months, one in late May and one in late August following a trip to Nebraska to see the weed for ourselves.

Farmers in much of the country already are dealing with Palmer amaranth, which weed scientists have voted "America's No. 1 weed enemy." Weeds aren't partial to a certain type of farmer, and, like Palmer amaranth is doing, they spread.

Native to the southwest U.S., the weed is spreading east and north. It's now established in parts of the Corn Belt and has been found in southern Minnesota and parts of South Dakota. Experts say it almost certainly will spread to the rest of the Upper Midwest, too.

Weed scientists dislike the term "super weed," and we're reluctant to use it. But Palmer amaranth possesses a combination of characteristics that make it particularly potent. Here's a partial list:

• Each Palmer amaranth plant can produce as many 1 million seeds. What's more, the seeds are so small that farmers can spread them unknowingly.

• Seeds can lie dormant in the soil for years, waiting to germinate until growing conditions are favorable.

• The seeds are extremely competitive with other crops, including corn and soybeans. Yield losses of up to 91 percent in corn and 79 percent in soybeans have been reported.

• It can grow up to 3 inches per day and becomes harder to control the bigger it gets. It can reach more than 10 feet high, towering above mature corn.

• It closely resembles pigweed and waterhemp, especially when small. So farmers may misidentify it and take inadequate steps to control it.

• It's prone to developing herbicide resistance. Each weed produces so many seeds and new plants that at least a few are likely to survive herbicide application — and those survivors, in turn, are more resistant to herbicide.

Reading about Palmer amaranth gives agriculturalists an idea of how dangerous it is. But the threat cannot be fully understood until they see the weed in person.

A group of North Dakota agriculturalists, primarily extension officials, recently visited Nebraska to learn more about the weed. The trip was funded by the North Dakota Soybean Council. Jonathan Knutson, Agweek's 27-year veteran reporter, and Nick Nelson, Agweek photojournalist, attended.

The group saw fields infested with Palmer amaranth, fields in which the weed was first seen only a few years ago. Farmers had made a determined effort to control with chemicals. The group learned first-hand that early detection and a broad-based approach are needed to keep the weed in check.

We can't overstress the importance of not relying on herbicides to deal with Palmer amaranth. If you're counting on industry to develop a new chemical that single-handedly licks the weed, you're making a tragic mistake, experts say.

There's a tendency, even among agriculturalists, to think, "Ho-hum. Just another weed" when they hear about Palmer amaranth. But the threat is real. It's huge. And it's immediate.

Our recommendation? Learn as much as you can about this terrible weed. Best educate and prepare yourself for a long, difficult and must-win battle against it.