original-india together THE BOLLWORM RETURNS
Is Bt-based resistance collapsing?
Studies from China and the US show the limitations of Bt-based resistance. The bollworm evolves to resist the toxin eventually, and a number of secondary pests remain unaffected. Suman Sahai argues that this is not really a workable strategy except in the first few years.
24 February 2007 - A recent study from China, reported at the American Agricultural Economics Association's annual meeting in July 2006, indicates that the Bt cotton crop there is failing, and farmers are incurring losses rather than making profits from its cultivation. The study, conducted by Cornell University, found that Bt cotton farmers cut pesticide use significantly for the first three years of cultivation. After that, however, they had to spray just as much as conventional farmers, and ended up with a net average income of 8 percent less than conventional cotton farmers, partly because the cost of Bt seed is triple that of conventional seed. Also, after seven years of Bt cotton, populations of other insects - such as mirids - have increased so much that farmers now have to spray their crops up to 20 times in a growing season. The Cornell researchers anticipate that the emergence of secondary pests is likely to become a major threat in countries where Bt cotton has been widely planted.
Published at almost the same time as the China study, other reports from Arkansas in the United States (see here) show that bollworm were found to be feeding in large numbers in Bt cotton fields. These pests should have been killed by the toxin that is engineered into the plant to kill them, and their presence indicates they may have become immune to the genetic treatment. This breakdown is happening roughly ten years after Bt cotton was first planted there. Unlike in Arkansas, the problem in China is not due to the bollworm developing resistance to Bt cotton. Instead, secondary pests - that were previously controlled by the broad-spectrum pesticides that were common earlier - began reappearing with the shift to gene-based control.
In India an ad hoc research agenda, in the absence of any policy on genetically engineered crops, has led to wide use of the Bt gene. Over forty two per cent of the research projects in crop biotechnology in India are based on the Bt gene. Ranging from cotton to potato, rice, brinjal, tomato, cauliflower, cabbage, even tobacco, to maize, the Bt gene is everywhere.
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complete article including links to the arkansas report
here
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