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By Dan Gunderson
August 21, 2000
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RealAudio 3.0 |
Agriculture changed forever in 1946 when the first herbicide, 2-4D, was introduced. Easy weed control meant higher-yielding crops and less work for farmers. Many thought the endless battle against weeds was over, but in a growing number of cases, 54 years later the weeds are winning.
IN THE PAST 20 years, scientists and farmers have identified more than 200 herbicide-resistant weeds. About 80 resistant species are now found in Minnesota.
At Joe Hastings' farm near Felton Minnesota an all-day rain is interrupting the fall harvest. Hastings is among dozens of farmers in Minnesota and North Dakota dealing with one of the most troublesome herbicide-resistant weeds. Kochia is a bushy plant that grows about three feet high and produces thousands of seeds. Anyone driving through farm country in the fall has likely seen it rolling across fields and roads.
In its dried form, it's commonly known as tumbleweed.
Joe Hastings says he first saw kochia two years ago and since then it has spread rapidly.
"You can tell where the resistant kochia plant in the fall has bounced across the field. You can see a line of plants that are resistant to the chemicals we're using. An actual straight line or however the wind blew it, but its a pattern where a kochia plant blew across in the fall, broke its stem and was a big tumbleweed going across and scattered seed all across as well."
Last fall researchers at North Dakota State University in Fargo collected kochia seed from sugarbeet fields in the Red River Valley and southern Minnesota. This year they planted those seeds in a greenhouse and applied the only herbicide that can be used on kochia in sugarbeets.
NDSU and University of Minnesota weed specialist Alan Dexter says 98 percent of the plants survived.
"Resistant kochia is potentially a very serious problem because at this point we don't have any good control methods that are effective and affordable."
Dexter says to save money, farmers use the cheapest effective herbicide year after year. Repeated exposure speeds the development of resistant weeds. As a result, kochia has developed immunity to an entire family of herbicides widely used on a variety of crops.
Alan Dexter says in the past 20 years, as resistant weeds evolved , scientists developed new chemicals to control them. He says depending on chemical companies to solve the problem is dangerous.
"I think many of our growers are believing that's going to happen," Dexter said. "They can use up these old herbicides and so if they quit working they'll just switch to something new, but we don't know if new things are always going to be coming along. We may run out of new active ingredients or new modes of action to take care of some of these problems."
Dexter says sugarbeet farmers may be forced to return to some old techniques. Migrant farm workers with hoes may be the only solution to these herbicide-resistant weeds. In the past five years most farmers have found that chemical herbicides are more cost-effective than migrant laborers.
Dexter says while kochia is the most serious problem, he's also concerned about an apparent increase in resistant wild oats this year. Researchers will gather seed and test those plants next year.
Scientists caution that the resistant weeds can still be controlled, but farmers need to be educated and change farming practices for all crops if they hope to avert a potential disaster.
Richard Zollinger is weed specialist at North Dakota State University and part of an international monitoring network. Zollinger discovered four new herbicide-resistant weed varieties last year. He says it's critical to avoid the worst case scenario, a weed developing resistance to all herbicides. So far, that's happened only in Australia.
"That's what we're scared of," Zollinger admits. "We're scared of weeds adapting and developing the ability to withstand many different kinds of herbicides. Mother nature is very crafty and very smart."
An international coalition of scientists is calling for a return to the weed control measures of yesteryear, including intensive tillage, animal grazing, burning and a greater variety of crops. The cost of these recommendations makes them unpopular with most farmers. Many farmers do, however, gamble on new compounds that will keep them one step ahead of herbicide-resistant weeds. Scientists agree that its a high risk gamble.
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