Why Grow GM Crops That Need Pesticides Anyway?
August 24, 2006
Chinese cotton growers were among the first farmers to plant genetically modified (GM), bollworm-resistant cotton. However, other pests have begun attacking the cotton in place of bollworms, casting doubt on the long-term usefulness of the GM plants.
The GM crop Bt cotton has a Bacillus thuringiensis gene inserted into the seeds. This gene makes the plants produce toxins that are deadly to leaf-eating bollworms.
But now other, so-called secondary pests, such as mirids, have increased in numbers to take the bollworms' place. Because of this, Chinese farmers are now having to spray their crops with pesticides up to 20 times a growing season.
The Bt cotton initially proved useful; after three years of using it, farmers cut their pesticide use by more than 70 percent, and were earning as much as 36 percent more than their peers as a result. After seven years, however, the GM farmers needed to spray just as much as conventional farmers.
Since the Bt seed costs three times the amount of conventional seed, farmers using the GM plant were making less money in comparison.
Bt cotton is widely used in the United States, China, India, Argentina, Mexico and South Africa. It is not yet known whether or not secondary pests will become a problem in countries other than China.