The benefits of growing genetically engineered cotton resistant to bollworm pests appear to have been eroded as new pests move in, a new study suggests.
The five million Chinese GM cotton farmers appear to have created a natural vacuum by growing cotton genetically engineered to kill the bollworm larvae which used to destroy their plants. With the bollworm larvae gone, other pests called mirids have taken over, forcing farmers to eradicate them with lashings of expensive insecticide that have all but destroyed the original economic benefits.
When GM cotton was first grown in China in the late 1990s, it produced miraculous results that were hailed as proof that GM technology could benefit poor farmers. They saw great gains – in the first three years of planting the crop called Bt cotton – they cut pesticide use by more than 70%.
But seven years down the line, mirids are spoiling the party to such an extent that the farmers have to spray their crops up to 20 times per growing season to control them.
Problems crop up
“The farmers are very upset about it, because GM cotton was such a wonderful thing, and they don’t understand why it won’t work now,” says Shenghui Wang of Cornell University in Ithaca, New York, US, who interviewed 481 Chinese farmers in 2004 about their more recent experiences with the GM cotton.
But Wang, who presented her results on 25 July in Long Beach, California, at the annual meeting of the American Agricultural Economics Association, insists that GM cotton should not be abandoned because of the latest setbacks.
“GM cotton has helped more than five million Chinese farmers. Over that period, up till 2004, farmers have really been much better off, and the environment has benefited,” says Per Pinstrup-Andersen, Wang’s supervisor. “It was a tremendous success story. But over time, things developed that must be dealt with, just as with other technologies. It doesn’t mean farmers shouldn’t use it.”
There are solutions, they say. The most immediate is for the Chinese government to encourage of the siting of non-GM cotton fields, or wildlife “refuges” in areas neighbouring GM fields. These fields attract the usual pests, including bollworm larvae, and have to be sprayed with powerful insecticides that would also keep the mirids in check.
Longer term alternatives include identifying and introducing natural predators of the mirids, or equipping GM cotton with new toxins that kill them as well.
Pinstrup-Andersen says the findings should also alert governments and researchers in other countries that have adopted the technology to take action, such as India and Argentina. The one good bit of news is that bollworm larvae appear not to have developed resistance to the GM cotton. “That is a plus,” says Pinstrup-Andersen.
(Cf. news of June 03, 2002.)
Source: NewScientist July 25, 2006.