GM cotton shows low pesticide use, safety: study

A genetically modified (GM) cotton with insect-killing toxic proteins may require less pesticide use while keep the overall crop yields, scientists reported on Monday.

This transgenic cotton, called Bt cotton, has been inserted a gene to produce Bacillus thuringiensis(Bt) toxin, a naturally occurring insecticide that kills the major cotton pest pink bollworm. The cotton has been planted in U.S. state of Arizona since 1996.

According to a latest research by scientists at the University of Arizona, for any given level of pesticide use, transgenic cotton had higher crop yields than non-transgenic cotton, and it showed no significant impacts on the biodiversity of non-target insects compared with natural cotton.

However, overall crop yields were similar, largely because the higher use of insecticides with non-transgenic cotton helped control important pests not controlled by Bt cotton, according to the researchers.

These findings, coming from the first large-scale study that simultaneously examined how growing Bt cotton affects yield, pesticide use and biodiversity, appeared in the May 1 issue of the Proceedings of the National Academy of Sciences.

Over two years, the researchers studied 81 commercial fields in a 6,600-sq-km region in Arizona, where natural cotton, and two strains of transgenic cotton were planted. They compared the yield and pesticide use for 40 fields of natural cotton, 21 fields of Bt cotton and 20 fields of Bt cotton that was also herbicide-resistant.

The researchers found that Bt cotton produced 9 percent more cotton per acre than natural cotton at the same level of pesticide application, but growers that planted Bt cotton used fewer applications of broad-spectrum pesticides.

As a result, growers ended up with similar yields regardless of the type of cotton grown.

The yields were similar across cotton types because the additional insecticide applications on the non-Bt fields cut down on the damage from whiteflies and western tarnished plant bugs, the researchers indicated.

The results suggested that transgenic cotton may help reduce the negative impacts of agricultural intensification such as fertilizers and pesticides, but important pests not targeted by the transgenic cotton could be otherwise controlled, they said.

"The take-home message is that transgenic crops are very promising for reducing the impact of agriculture," said Yves Carriere, an associate professor at the University of Arizona who led this study.

"But we need to study how they're integrated into the way we do agriculture. It depends on how the producers react to the technology," he added.

Source: Xinhua