The U.S. government this week approved a new strain of genetically altered corn that promises to reduce the amount of chemical insecticide farmers spray. The new maize strain is the latest example of the revolution in biotechnology. Despite concerns among critics about possible health or environmental impacts, biotech crops have become common on American farms. A recent study of a genetically modified cotton crop's performance in India, has raised hopes that its benefits could aid the developing world.

Every year, farmers spray more toxic chemicals on cotton than on any other crop to protect their fields from hungry bugs. In high doses, these chemicals can poison farmers and the environment.

Agriculture companies, like Monsanto, have used biotechnology to create a strain of cotton that produces its own natural insecticide, a protein called B-t. B-t is toxic to an insect pest called the bollworm, but harmless to people, birds, fish, and even most other insects.

B-t cotton caught on quickly among American farmers when it was introduced in 1996. Today, it makes up about a third of the American cotton crop.

Monsanto introduced the technology into India's commercial market last year, after four years of field tests. Monsanto spokeswoman Ranjana Smetacek says farmers using B-t cotton are using less insecticide and getting bigger yields than with regular cotton. "The success of B-t cotton, in our minds, is undoubted."

A study of B-t cotton published in the journal Science last month backs that up. The researchers, who conducted four years of field tests, found the B-t variety required 70 percent less insecticide and produced an average of 60 percent more cotton than the regular plant.

In 2001, when farmers in India faced what Ms. Smetacek called an epidemic of bollworms, the B-t crops outperformed by 80 percent or more, according to the study.

Farming consultant Chuck Benbrook agrees that B-t cotton can reduce toxic chemical usage, while also reducing crop losses to insects. But he says the study exaggerates the benefits, because bollworms are not the only problem that growers face. "There are often other insect pests in a cotton field and other things that growers have to do to keep crop losses at a minimum," he says. "So, I think, there were conclusions reached that do not really apply to the real world."

Mr. Benbrook is also concerned about the cost of the B-t cotton seeds. They are about three to four times more expensive than regular seeds.

Monsanto's Ranjana Smetacek says the extra expense is worth paying, because the farmer gets more crop for the money. "We've found with most agricultural technologies, the incremental benefit that he (the farmer) derives, about a third of it, he is prepared to pay back to the technology provider," she says.

Michael Hansen of the U.S.-based advocacy group Consumers' Union, says farmers had some problems with the technology in its first year in India. For example, in some cases, he says, farmers got only slightly more cotton than before. "But they had spent so much more for the seeds, that they did not end up making any more money," he says.

Experts say insect problems are often more severe in the tropical countries of the developing world. Conventional insecticides may also be harder to come by in these countries. So the study's authors say B-t cotton, as well as other B-t crops, like corn and potatoes, can provide greater benefits there than they can in the more temperate climates of the developed world.

But critics say that is too broad a conclusion to draw from this limited study of one crop.