By RICK A. RICHARDS
Indiana Correspondent

HANNA, Ind. — The effects have been gradual, but in the 28 years since Greg Werner joined his father’s farming operation, he’s become aware that some weeds are more tolerant of herbicides.
He and his father, Otto, farm 1,800 acres of corn, soybeans and wheat near the small town of Hanna in southern LaPorte County. “We also do a fair amount of custom cultivation” said Werner, adding the farm is a seed and fertilizer dealer.

When talk began circulating about so-called “super weeds” that were resistant to products that contained glyphosate (commonly found in Roundup), Greg paid close attention. Since the Werners are 100 percent no-till, the farm depends on the use of chemicals to burn off weeds before crops emerge.

“We found out it was the widespread use of Roundup on corn and soybeans that was causing the problem,” said Greg, adding he and his father have been supplementing the use of Roundup with other chemicals such as 2, 4-D which has so far kept the problem of chemical-resistant weeds on their farm in check.

“So far we haven’t seen anything,” said Greg. “I think the problem in this area is mostly in isolated areas, and it’s in southern and central Indiana.”

But Scott Swinton, a professor of agricultural, food and resource economics at Michigan State University, said that doesn’t mean the Werners – or any other farmers, for that matter – should relax. He said farmers should study weeds on their farms just as closely as they study their crops. He said farmers should know where weeds grow, how they grow, if they are spreading and when they germinate.

Some of the weeds, said Swinton, are easy to control, which means farmers may not have to take drastic steps to eliminate them. But the key suggestion from Swinton is that farmers need to regularly change herbicides and rotate their crops.

An ally for farmers in the fight against chemical-resistant weeds is WeedSoft, a computer program that can help growers determine which herbicide is most effective in eliminating the weeds on their farm.

The ones causing the biggest problem in Indiana, said Glenn Nice, an extension service weed professional at Purdue University, are marestail and giant ragweed. But there are others, including Johnsongrass, shattercane, jimsonweed, lambsquarters and pigweed.

“It is a problem everybody needs to be aware of,” said Nice, adding he thinks it’s sensationalizing to call them “super weeds.”
“I wouldn’t go that far,” he said.

Even so, Nice said glyphosate is used just about everywhere and he thinks it’s responsible for creating a problem in “natural selection.”
Monsanto developed glyphosate and it became popular because it could be sprayed during planting and wouldn’t affect corn or soybeans as they emerged. While glyphosate itself isn’t a problem, its overuse is. Nice compared the overuse to that of the family doctor who over-prescribes penicillin for a cold, enabling that virus to build up a resistance to treatment.

Nice said glyphosate is effective in killing most weeds, but if applied when weeds are more than six inches tall, it isn’t effective. As a result, seeds left after the harvest will have a resistance and be harder to kill the following spring.

“Plants are no different than any other living system that builds up a resistance to a drug,” said Nice. “The continuous use of a single action like the application of glyphosate puts pressure on the selection process that can result in resistance.

“It’s not the chemical that’s causing the problem; our research shows it’s the plant. What we’re doing is killing all the susceptible plants and leaving the resistant ones.”

The key to breaking that cycle, said Nice, is to mix up the application process and apply something like 2, 4-D to supplement glyphosate. The drawback to that is farmers have to wait seven days before planting. Another option is an application of saflufenacil in place of 2, 4-D, but it’s a more expensive product.
“Farms are a business and farmers have to run them as a business,” said Nice, adding that a decision not to add a second chemical may be based solely on a short-term bottom line issue and not a long-term look at the impact on a field.

Bill Johnson, a professor of botany and plant pathology at Purdue, has spent years studying chemical resistant weeds. He said the biggest problem in Indiana is marestail, a weed that can easily take over a field. It can grow quickly and crowd out a crop by draining the soil of the nutrients corn or soybeans need to grow. In 2005, he said glyphosate-resistant marestail was found in 40 of Indiana’s 92 counties.

“Realistically, today it’s probably in all of them,” said Johnson. As for giant ragweed, he said resistant plants have been found in 14 counties, and the problem is probably more widespread than that.
Johnson said his research shows it can cost anywhere from $1-$7 an acre more to control chemical-resistant weeds, with nearly all of that cost because of the application of a second chemical.

Marestail was the first glyphosate-resistant weed found in the United States, in Delaware in 2000. It appeared in Tennessee in 2001 and in Indiana, Maryland, New Jersey and Ohio in 2002. According to the International Survey of Herbicide Resistant Weeds, some 7 million-10 million acres are affected in the U.S., out of a total of 170 million acres of corn and soybeans.

Brian Glass, plant food manager at the Starke County Co-Op in Hamlet, Ind., said he’s heard of the problem, but isn’t aware of any resistant weeds in his area.

“We usually don’t see weeds like that with what we do, but the problem comes when chemicals aren’t applied at the full rate or areas of a field are missed,” he explained.