EXTRACT: The spread of the resistant Johnson Grass could increase agricultural production costs by 500 million to 3 billion Argentine pesos ($160-$950 million) per year, according to Cantero. Combatting the strain will require the use of 25 million liters of herbicides other that glyphosate each year, he said.

"This could double herbicide costs in the effected areas," Senasa's Ploper said.

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"Isolated cases have been confirmed in Salta, Tucuman, Corrientes, Santiago del Estero, Cordoba and Santa Fe provinces," Ploper said. The glyphosate- resistant weed, known as sorghum halepense, or "Johnson Grass," had previously been confirmed only in Salta and Tucuman provinces.

The government has launched a number of projects to control the spread of the weed, including the use of herbicides other than glyphosate and attempting to mandate cleaning of harvest machinery to prevent spreading the weed between fields, Ploper said.

In addition, Cordoba province Congressman Alberto Cantero introduced a bill this week aimed at eradicating the glyphosate-resistant weed.

Last year, some 120,000 hectares were effected by the resistant weed, according to Cantero. "The invasion is developing rapidly and we are possibly in the beginning phases of the (widespread presence) of this plague," Cantero said in the bill.

The spread of the resistant Johnson Grass could increase agricultural production costs by 500 million to 3 billion Argentine pesos ($160-$950 million) per year, according to Cantero. Combatting the strain will require the use of 25 million liters of herbicides other that glyphosate each year, he said.

"This could double herbicide costs in the effected areas," Senasa's Ploper said.

Around 98% of Argentina's soy crop comes from seeds developed by U.S. biotech giant Monsanto Company (MON). The soybeans have been genetically modified to resist the herbicide Roundup, generically known as glyphosate. The herbicide is applied to eliminate competing plant species and thus increase output per hectare.

In addition, at the end of August the government approved Monsanto's bundled MG and RR2 transgenic corn seed variety for planting in the 2007-08 season. The seeds are genetically modified to produce a substance toxic to corn borer parasites and for glyphosate resistance.

Monsanto has a small amount of the seeds ready for this year's crop, which will be used to test the technology, Monsanto Argentina spokesman Federico Ovejero said.

The company claims the new variety may boost corn yields by 5-7%. The seeds are expected to be widely used across the Pampas, further adding to the country's heavy reliance on glyphosate.

Monsanto's shares hit an all-time high Wednesday after a top executive said that within the next decade, the agriculture and biotechnology giant could triple the number of acres outside the U.S. being planted with its genetically engineered seeds.

"Strong global adoption of our proven traits coupled with recent approvals paves the way for expanded growth and sets the stage for new growth, as we look to stack and upgrade these products in the coming years," said Brett Begemann, executive vice president of Monsanto's global commercial business.

Argentina figures big in those plans, despite a bitter conflict over royalty fees. The company has been struggling for years to collect royalties on soybean seeds containing its gene for glyphosate resistance, which it introduced in 1996. However, the company has been unable to obtain a patent on the seeds or collect royalties from the majority of farmers.

The company has vowed not to make the same mistake with its second generation of Roundup Ready soybeans, which are easily held over and replanted. Transgenic corn seeds tend to lose their traits through the generations, ensuring that farmers will return to the company for seed supplies.

Only the U.S. produces more genetically modified crops than the South American country. Argentina has more than 17 million hectares dedicated to the production of transgenic crops, according to the International Service for the Acquisition Agri-Biotech Applications, or Isaaa, a non-governmental organization dedicated to the promotion of agricultural biotechnology.

After their introduction, Monsanto's beans quickly came to dominate Argentina's crop as they allowed more no-till farming, thus conserving topsoil and moisture and boosting yields. The country is now the world's third-ranked soybean producer and exporter and the leading soymeal and soyoil exporter.

However, there are concerns that other weed varieties resistant to glyphosate will develop due to the repeated use of the herbicide across Argentina's Pampas each season.

"We were actually surprised that it took so long (for the resistant Johnson Grass) to appear," Ploper said.

Signs of glyphosate-resistant sorghum halepense were first detected in 2004, according to the Argentine Fertilizer and Agrochemical Industry Chamber, or CIAFA.

The glyphosate-resistant strain developed through the process of natural selection following years of glyphosate spraying, according to Armando Allinghi, agricultural engineer at CIAFA.

Sorghum halepense may have originated in the Mediterranean area. The plant is known as "Johnson Grass" in the U.S., named after Col. William Johnson, who introduced it to Alabama in the 1840s for use as animal feed. It was introduced to Argentina for the same reasons and rapidly became a pest as took to the Pampas with a vengeance.

"It is one of the worst weeds ... (affecting) ... the subtropics throughout the world," according to the Food and Agriculture Organization of the U.N.

-By Shane Romig, Dow Jones Newswires; 54-11-4314-2757; This email address is being protected from spambots. You need JavaScript enabled to view it.