KANSAS CITY (Reuters) - The rapid adoption by U.S. farmers of genetically engineered corn, soybeans and cotton has promoted increased use of pesticides, an epidemic of herbicide-resistant weeds and more chemical residues in foods, according to a report issued Tuesday by health and environmental protection groups.

The groups said research showed that herbicide use grew by 383 million pounds from 1996 to 2008, with 46 percent of the total increase occurring in 2007 and 2008.

The report was released by nonprofits The Organic Center (TOC), the Union for Concerned Scientists (UCS) and the Center for Food Safety (CFS).

The groups said that while herbicide use has climbed, insecticide use has dropped because of biotech crops. They said adoption of genetically engineered corn and cotton that carry traits resistant to insects has led to a reduction in insecticide use by 64 million pounds since 1996.

Still, that leaves a net overall increase on U.S. farm fields of 318 million pounds of pesticides, which includes insecticides and herbicides, over the first 13 years of commercial use.

The rise in herbicide use comes as U.S. farmers increasingly adopt corn, soy and cotton that have been engineered with traits that allow them to tolerate dousings of weed killer. The most popular of these are known as “Roundup Ready” for their ability to sustain treatments with Roundup herbicide and are developed and marketed by world seed industry leader Monsanto Co.

Monsanto rolled out the first biotech crop, Roundup Ready soybeans, in 1996.

Monsanto officials declined to comment on the report. But the Biotechnology Industry Organization, of which Monsanto is a member, said the popularity of herbicide-resistant crops showed their value outweighs any associated detriments.

“Herbicide resistance crops are incredibly popular with farmers. They help them manage their weed problems in ways traditional crops don’t,” said Mike Wach, BIO managing director of science and regulatory affairs.

“If a farmer feels a crop is causing them more trouble than it is worth they will stop using it,” Wach said. “Farmers are continuing to adopt these crops because they provide benefits, not liabilities and problems.”

BIO officials pointed to a report issued earlier this year by PG Economics Ltd that said the volume of herbicides used in biotech soybean crops globally decreased by 161 million pounds, or 4.6 percent, from 1996 to 2007.

The report by the environmental groups states that a key problem resulting from the increase in herbicide use is the emergence of “super weeds,” which are difficult to kill because they have become resistant to the herbicides.

“With glyphosate-resistant weeds now infesting millions of acres, farmers face rising costs coupled with sometimes major yield losses, and the environmental impact of weed management systems will surely rise,” said Charles Benbrook, chief scientist of The Organic Center.

The groups additionally criticized the agricultural biotechnology industry for claiming that higher costs for genetically engineered seeds are justified by multiple benefits to farmers, including decreased spending on pesticides.

The group said biotech corn seed prices in 2010 could be almost three times the cost of conventional seed, while new enhanced biotech soybean seed for 2010 could be 42 percent more than the original biotech version.

“This report confirms what we’ve been saying for years,” said Bill Freese, science policy analyst for the Center for Food Safety. “The most common type of genetically engineered crops promotes increased use of pesticides, an epidemic of resistant weeds, and more chemical residues in our foods. This may be profitable for the biotech/pesticide companies, but it’s bad news for farmers, human health and the environment.”