NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
January 6, 2000
Herbicide-resistant kochia once was a problem only in western North Dakota, but it since has become established in the Red River Valley. Prior to 1999, the list of documented herbicide-resistant weeds comprised only kochia, green foxtail and wild oat. Now that list also includes nightshade (black and eastern black), water hemp and wild mustard.
While news that the confirmed number of North Dakota's herbicide-resistant weeds has suddenly doubled is certainly alarming, there is no need for panic, because there are registered products available that will control these weeds. What producers will need to do is re-think their weed-control strategies, says a researcher with the Department of Plant Sciences at North Dakota State University.
"Look at all the options available, because you're going need every tool out there," says Richard Zollinger, extension weed specialist at NDSU.
Black nightshade and eastern black nightshade have become problem weeds for North Dakota row-crop producers primarily due to the wet weather of recent years, Zollinger says. To control these broadleaf weeds, producers have been relying on Pursuit in soybeans and Raptor in dry edible beans. Pursuit and Raptor belong to the group of herbicides collectively known ALS inhibitors.
ALS herbicides act on specific enzymes to prevent the production of specific amino acids, which are key building blocks for normal plant growth and development, Zollinger explains. Along with Pursuit and Raptor, other ALS products include Accent, Ally, Amber, Assert, Beacon, Broadstrike, Classic, Express, Harmony Extra, Matrix, Pinnacle, Scepter and Upbeet.
Zollinger says, "Last fall, we discovered three or four fields in northern Cass County where the nightshade had become resistant to Pursuit and Raptor. Now, this is just an isolated spot, but my point is that if it happens once, it could occur in other areas."
Water hemp, a member of the pigweed family, has a natural tolerance to ALS herbicides. Zollinger says water hemp develops a deep red or purple coloration as it matures and is easy to distinguish from redroot pigweed. He adds, "All the reports had indicated that water hemp is more of a Kansas-Nebraska weed. We thought that maybe our winters were too harsh or that our crop rotations were preventing this weed from establishing this far north. But we do have it. It's very well entrenched on both the North Dakota and Minnesota side of the Red River Valley. It's going to be a problem."
Likewise, wild mustard is showing resistance to ALS herbicides. Zollinger says the discovery of the resistant wild mustard was on 320 acres in Cass County and marks the first documented case in the United States.
"Hopefully, we can contain the resistant wild mustard so it doesn't move from that site," Zollinger adds.
Because the newly documented cases of herbicide resistance all involve ALS herbicides, producers with these types of resistant weeds will need to switch to herbicides with other modes of action. In soybeans, producers now have the option of using Authority, a new herbicide that is highly effective at controlling kochia, nightshade and water hemp. Zollinger says that same herbicide, available as Spartan, is labeled for sunflower.
"Producers who've got reason to believe they've got resistant weeds should put down foundation herbicides that will keep that population in check," Zollinger concludes. "Put down a soil-applied herbicide with a good eight-weeks residual, so you take the weeds out right from the get-go."
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Source: Richard Zollinger (701) 231-8157
Editor: Dean Hulse (701) 231-6136