Weeds Developing Resistance To Widely Used Herbicide

By Scott Canon
The Kansas City Star
August 20, 2001

As weeds go, it looks so ... common.

Broad but not huge leaves. A stalk that runs from pure green to half crimson, but never eye-catching.

Could this scrawny member of the pig weed family have stumbled upon the herbicide-resisting powers that agri-giant Monsanto implanted in crops only after years of laboratory gene tinkering?

Is this, the humble amaranthus tuberculatus, a superweed?

"Right now, I'm just calling it insensitive," said Reid Smeda, a University of Missouri-Columbia weed scientist.

He's studying whether a strain of water hemp -- no relation to the stuff used for rope or dope -- plucked from northeast Missouri and west-central Illinois can shrug off the popular herbicide glyphosate.

Weeds overcome herbicides all the time. But glyphosate, best-known as Monsanto's Roundup brand, kills virtually everything green.

That's why genes were custom-fitted into crops specifically to withstand the weed killer king. With such seeds, a farmer can plant a genetically modified crop, spray with glyphosate and expect all the pest plants to whither while grain grows unharmed.

Farmers, in fact, love the simplicity of it all.

Such trademarked Roundup Ready varieties account for four out of every five American acres planted with soybeans. Roundup Ready corn, canola and cotton have been popular as well. Monsanto soon could offer herbicide resistance in sugar beet, rice, wheat and lettuce. Already, the technology is locked solidly into the nation's food chain.

Water hemp could ruin all the fun.

It could, in fact, fulfill the prophecy of environmentalists that widespread use of herbicide-resistant crops eventually will lead to the rise of herbicide-resistant weeds -- breeds of super weeds.

"Given enough generations and enough exposure, any species will develop resistance to a herbicide," said Rebecca Goldburg, a senior scientist for anti-biotechnology Environmental Defense.

Monsanto is more than skeptical. David Heering, the company's lead expert, disagrees with the theory that continued use of Roundup Ready crops inevitably will lead to superweeds.

"I would challenge anybody," he said, "who says they're going to predict weed resistance to herbicides."

'The U.N. of plants'

So far, water hemp has given only an inkling of Roundup resistance. Native to the Grain Belt, it is the most common weed in Missouri soybean fields and is on the way to being the most common weed in the state's corn fields.

Its genetic background is highly diverse -- "It's the U.N. of plants," Smeda said -- and that increases its chances of coming up with a strain that will resist what farmers throw at it.

In 1999, a farmer near Monticello, Mo., and another near Sutter, Ill., reported that some water hemp was shocking them by surviving glyphosate, albeit at low rates.

Both locations were Roundup Ready soybean fields treated season after season with glyphosate.

At first skeptical, Smeda collected samples for dousing in herbicide at his University of Missouri-Columbia greenhouse along with tests in the field.

In both settings, he found that some water hemp plants survived sprayings of glyphosate -- sold as Roundup, Touchdown, Glyphomax, Glyphos -- at higher rates than other weeds.

In greenhouse conditions, 4 percent to 5 percent of the suspect water hemp plants survive sprayings with glyphosate, almost regardless of the dosage.

"Under those conditions, you'd expect a 100 percent kill," Smeda said.

He's puzzled, however, because the offspring of those survivors demonstrate the same 5 percent survival rate, when science might predict them to inherit their parents' sturdier character.

Smeda thinks farmers will need to rotate their herbicides, which would mean planting something other than Roundup Ready crops.

"The Roundup Ready technology is so good, we don't want to lose it," Smeda said.

Another pest

In Delaware, weed scientist Mark VanGessel has a horseweed, commonly known as mare's tail and categorized scientifically as conyza canadensis, that appears to have whipped glyphosate.

When he first got reports from around the state of resistance in 1999, VanGessel admits he was dismissive.

Dousing samples with glyphosate, he found to his own surprise that "it stunts them, but it won't kill them."

"Farmers had been using Roundup for 25 years, and there was no resistance yet," said VanGessel. "It turns out the operative word was 'yet."'

But those decades before Roundup Ready was introduced five years ago were different. Glyphosate was used in rotation with other weed killers, depending on the weed problem, and the timing of planting cycles. With new gene-spliced designer Roundup Ready soybeans, however, there seemed little reason not to use glyphosate exclusively.

The problem, say agronomists, is that continually killing off the herbicide weaklings leaves less competition -- for nutrients in the soil, for water, for light -- for that random genetic mutation that can weather a rain of Roundup.

"This is kind of a wake-up call that we can't rely on glyphosate year in and year out for weed control," VanGessel said.

Monsanto greets such reports with skepticism. The company's patent on glyphosate expired Sept. 20, 2000. But it continues to sell the herbicide and license the sale of Roundup Ready seed.

Roundup is much more environmentally friendly than other popular herbicides. Atrazine, for instance, can pose a problem for soil and water pollution years after it is first applied. Evidence of glyphosate use, in contrast, can disappear in a matter of days.

Heering, Monsanto's expert, concedes that goose grass in Malaysia and rye grass in Australia have shown resistance to glyphosate. But that has nothing to do with Roundup Ready crops. There, glyphosate is used like other traditional weed killers, without any coordination with genetically altered seeds.

Even there, he said, the company is making recommendations about mixing Roundup with other varieties.

As for the mare's tail and water hemp, Heering is not ready to concede. The company reads the data on water hemp to detect no resistance and is awaiting some tests of the mare's tail.

The consensus among weed experts holds that if water hemp hasn't developed resistance to Roundup, some other American weed eventually will. Mare's tail, insists VanGessel and others, already has. Farmers then will be forced back to changing their herbicide from one year after the next or risk fields choked with superweeds.

"The simplicity of the Roundup Ready system is not going to last very long," said Dale Shaner, a co-author of Herbicide Resistance and World Grains. "Most simple systems just don't stand up. Mother nature has a way to get around that."

Still others concede that if Roundup is destined for a showdown with superweeds, it holds a considerable edge now.

"There's a lot of (Roundup) being used," said Michael Christoffers, a weed geneticist at North Dakota State University. "If it were easy for weeds to develop resistance to it, we'd be seeing that happen much more often."

Related link: GM Crops Failed

Report Points Out Problems With Roundup Ready Soybeans

(May 3, 2001 -- Cropchoice news) -- Contrary to the promises of Monsanto, farmers are applying more herbicides to Roundup Ready soybean plants and reaping lower yields from them compared to conventional varieties, according to a new report by Dr. Charles Benbrook of the Northwest Science and Environmental Policy Center in Sandpoint, Idaho.

The study, "Troubled Times Amid Commercial Success for Roundup Ready Soybeans: Glyphosate Efficacy is Slipping and Unstable Transgene Expression Erodes Plant Defenses and Yields," available at http://www.biotech-info.net/troubledtimes.html uses recent USDA and university research to update the Center's 1999 report on the same subject.

Many farmers have told Cropchoice about the extra herbicides and lower yields that go along with growing Monsanto's herbicide-resistant beans. Despite this, they're planting more Roundup Ready soybeans -- 60 percent of this year's crop -- because the technology makes weed management relatively easy.

But what farmers may not want to hear, and what this study reveals, is that relying on Roundup to kill weeds in Roundup Ready soybean fields has led to their becoming herbicide resistant.

Increased herbicide use

One must look at the amount of herbicide growers apply per acre of soybeans to see that Monsanto's transgenic varieties require more applications, according to the executive summary of the report.

"More than a dozen soybean herbicides are applied at an average rate of less than .1 pound active ingredient per acre. Roundup, on the other hand, is usually applied on soybeans at about .75 pound per acre in a single spray and most acres are now treated more than once," Benbrook writes. "...Total herbicide use on RR soybeans in 1998 was 30 percent or more greater on average than on conventional varieties in six states, including Iowa where about one sixth of the nation's soybeans are grown. RR soybean herbicide use was 10 percent or more greater in three more states. Use on RR soybeans was modestly lower in five states."

Benbrook predicts that farmers will apply about .5 pounds more herbicide (active ingredient) to the average acre of Roundup Ready beans than they will to conventional varieties in 2001. "As a result over 20 million more pounds of herbicides will be applied this crop year."

Yield drag in Roundup Ready beans

The report highlights research linking the 5 to 10 percent yield drag in Roundup Ready soybeans to the interaction of their genetics with environmental factors, including the application of Roundup.

Herbicide resistance in weeds

"There are two major factors on the plus side of RR soybean trade-offs --weed management is simplified and soybean crop injury is avoided. But troubled times lie ahead for RR soybeans because the efficacy of glyphosate is clearly slipping in managing weeds and because unanticipated yield penalties are surfacing in some RR fields...," Benbrook writes.

GM Soy And Potatoes: Leaving their mark on the soil?

Cropchoice News
January 3, 2001

Researchers at the University of Missouri have concluded that spraying the herbicide Roundup (glyphosate) on soybean plants increases fungi in the surrounding soil, which might reduce growth and yield. Meanwhile, researchers in Germany found that GM potatoes may alter soil conditions, as well.

When Roundup Ready soybeans receive the dosages of Roundup that Monsanto the company that genetically engineers the soybeans and produces the herbicide recommends, the Fusarium fungus develops significantly faster than non-sprayed soybeans, reported Pat Donald, MU plant pathologist, and Robert Kremer, an MU soil scientist and USDA Agricultural Research Service microbiologist.

"There is a natural ebb and flow, but with Roundup Ready beans treated with Roundup, there was always a spike in the levels of the fungi studied," Kremer reported.

The concern for farmers is that elevated levels of Fusarium (some is common in all soybean fields) could lead to sudden death syndrome and other root rot diseases that reduce yields.

The scientists emphasized that their research did not show a reduction in soybean yields from the application of glyphosate as opposed to conventional herbicide treatments. However, potential yield impacts in subsequent seasons due to high soil Fusarium populations, resulting from continued use of glyphosate, needs further investigation."

It's worth noting that more than half of Missouri's soybeans are Roundup Ready. Meanwhile, traders are worried about a record soy crop in South America. Brazil, which does not grow GM soy, could weigh in with a 35.3 million ton crop, according to Safras e Mercado.

Across the Atlantic, researchers at the Max Planck Institute for Soil Microbiology in Marburg, Germany found that planting genetically modified potatoes alters the microbial villages in the soil. Although it's hard to say whether these changes are detrimental to future plantings on the site of the GM crop, the researchers favor the precautionary principle. This would mean removing the GM potato plants from the field until someone can evaluate the impact of the ecological alteration.

Sources: Doane, Positive News

Study Points To Problems With Genetically Engineered Cotton

Cropchoice News
January 9, 2001

A recent study raising possible concerns for farmers about genetically modified cotton has received much less attention than the seed and chemical companies' endorsement of transgenic technology.

Scientists writing in the Journal of Cotton Science point out some potential concerns with cotton that's genetically modified to resist the tobacco budworm and the herbicide glyphosate, also know as Roundup. Researchers found that the transgenic cotton they studied was less resistant to root-knot nematode, a serious cotton pest. Farmers typically control nematode infestation by planting different types of traditional hybrid seeds.

Despite this study, the StarLink debacle, consumer concerns about genetically engineered foods and fibers, and European and Japanese opposition, the International Cotton Advisory Committee recently reported that, the GE cottons approved pose no risks to human or animal health, the environment or natural biodiversity, and in that regard, are no different than conventionally produced cotton."

Phil Wakelyn, chairman of the Committee and senior scientist with the National Cotton Council, predicts that 50 percent of the world's cotton acreage will be of genetically engineered cultivars within five to seven years. That's a 12 percent increase over the numbers today. Wakelyn says that U.S. genetically modified cotton acreage will be much higher.

Of course, cotton farmers do not have to prove this prediction true. They can insist on planting only non-genetically engineered varieties.

Sources: Rooster.com, Journal of Cotton Science

GM Crop Toxin Is Leaking Into The Soil

By Nick Nuttall, Environment Correspondent
The Times
Thursday, December 2, 1999

Some genetically modified crops are leaking powerful toxins from their roots into the soil, scientists have found.

Researchers described the findings as "surprising and unexpected", raising fresh fears about the environmental impact of such crops.

Companies have modified plants to produce poisons or toxins to combat the pests that eat their stems and leaves. But the discovery that the same plants are also leaking toxins into the soil has not, until now, been considered an issue.

It will raise fears among some scientists, regulators and environmental groups that beneficial soil organisms might be killed and that insects living in the soil might become resistant to the poisons.

The findings, published today in Nature, have been released by a team at the University of New York that has been studying the roots of GM maize.

Several crops, from maize, to corn and potatoes, have been genetically modified to kill insect pests using a gene derived from a bacterium called Bacillus thuringiensis (BT). In the United States 15 million acres of corn modified with the BT gene were planted in 1998 or just under 20 per cent of the total crop. GM maize has also been planted in Europe although the acreage is far smaller.

Concerns about the impact of such crops on the environ-ment were triggered earlier in the year when it was found that monarch butterflies had died after feeding on milkweed dusted with pollen from GM corn.

Other research found that lacewings that had fed on corn borers reared on BT corn had also died, raising concerns that such crops are harming more than just pests.

Professor Guenther Stozky, of New York University's laboratory of microbial ecology, who has led the research, said yesterday that the monarch research showed that the toxin was released from the pollen.

"Now we have found it is also continuously released from the roots into the soil. The fact that the toxin is released from the roots was unexpected," he said.

Professor Stozky said that the BT toxin was a large protein molecule which they had considered too large to cross the root membrane.

During the research, the team grew GM seedlings in the laboratory for 25 days. Each plant produced on average 105 microgrammes of protein and this was tested against larvae of the tobacco hornworm. Up to 95 per cent of the larvae died after five days with 50 per cent killed at a dose of just 5.2 microgrammes of protein.

Because the roots are constantly leaking the toxin, there is also the risk that pests in the soil might rapidly become immune to the poison triggering new, resistant, strains.

Biotechnology companies are likely to claim that, because the bacterium from which the BT gene is taken, is found in the soil the toxin is naturally part of the environment underground. But Professor Stozky challenged such assertions, claiming that the bacterium was not prevalent in the soil.

Dr. Doug Parr, of Greenpeace said that the findings underscored the "ability of GM crops to wrong-foot their creators and produce unexpected and unwanted effects".

Dr. Penny Hirsch, a soil expert at lACR-Rothamsted in Harpenden, Hertfordshire, said yesterday that the findings were "interesting" but added that field tests were needed to see whether the effects in the laboratory were happening in the real world.

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