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2-Plants: FAO paper fear invasion of "superweeds"



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TITLE:  Scientists fear invasion of "superweeds"
SOURCE: Reuters, by David Brough
DATE:   November 13, 2001

------------------ archive: http://www.gene.ch/genet.html ------------------


FEATURE - Scientists fear invasion of "superweeds"

ROME - Beware the invasion of the superweeds.

Scientists fear genetically modified (GM) crops, already under attack for 
allegedly creating "mutant" food, could also create plants that are 
resistant to herbicides and insects. These could germinate from a previous 
harvest, hampering weed controls. GM herbicide-and insect-resistant crops 
are being planted on millions of acres (hectares) of arable land, mainly in 
North America, but some scientists worry about their impact on the 
environment.

"There are several concerns about the consequences of development and 
deployment of transgenic herbicide-resistant and insect-resistant crops," 
the United Nations food body said in a paper on the risks and benefits of 
GM crops. "Objections to the use of these transgenic crops rest on several 
issues...such as: the potential transfer of genes from herbicide resistant 
crops to wild relatives, thus creating superweeds," the Food and 
Agriculture Organisation (FAO) said.

Media in Canada reported earlier this year that the country's expert panel 
on biotechnology said GM superweeds had invaded Canadian farms. Canola 
plants engineered to help farmers had instead escaped and crossbred with 
each other to form plants stronger than their parents. Most pesticides 
cannot kill these canola superweeds, which are growing in wheat fields 
where farmers don't want them.


POTENTIAL HAZARD

Herbicide-and insect-resistant crops may pollute the gene pool of 
conventional relatives growing in the same area or nearby, depending on the 
wind and insects, the FAO says. "If there is no barrier to pollination, you 
get this potential hazard," Ricardo Labrada Romero, the FAO's weed and 
plant protection officer, told Reuters in an interview. "If, say, you are 
rotating maize with soybeans, you may find herbicide-resistant maize 
growing in a soybean field one year." The development of superweeds 
increases the need for additional labour to weed by hand and rid fields of 
unwanted plants that compete with the food crop, reducing its yield. "Weeds 
compete with crops for water, nutrients and light and are responsible for 
up to five percent of crop losses in developed countries," Labrada Romero 
said.


SAVINGS POSSIBLE

The benefits of genetically modified crops are mainly economic as farmers 
need to use less herbicides or insecticides. "With herbicide-resistant 
crops, you use less tractors, less fuel and implements," Labrada Romero 
said. James Dargie, a director of the FAO's agriculture department, told a 
recent seminar in Stockholm that use of GM crops in the United States had 
put the savings on weed control by U.S. farmers at $15 per acre (0.4 
hectares). "One estimate puts the overall reduction in pesticide use within 
the United States at 1.2 million kg (2.646 million lbs) per year, 
suggesting significant environmental benefits," he said.

This month, the U.S. Environmental Protection Agency (EPA) approved for a 
further seven years the use of corn genetically modified with Bacillus 
thuringiensis (Bt), a naturally-occurring soil bacterium that produces a 
protein toxic to certain insects. Incorporating the genetic material from 
Bt into corn plants enables them to produce the same toxin and defend 
against several species of pest. The EPA rejected claims by some scientists 
that Bt harmed local Monarch butterfly populations. "The scientific 
evidence demonstrates that Bt corn does not impact Monarch butterfly 
populations," the agency said. "Bt corn has been evaluated thoroughly by 
EPA, and we are confident that it does not pose risks to human health or to 
the environment," it added. "Farmers can continue to use an effective, low-
risk pest control alternative, which helps to protect the environment by 
reducing the amount of conventional pesticides used."



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