What is Bt cotton?

Published : Jun 06, 2003 00:00 IST

BACILLUS thuringiensis or Bt is a naturally occurring soil bacterium used by farmers to control Lepidopteran insects because of a toxin it produces. Through genetic engineering, scientists have introduced the gene responsible for making the toxin into a range of crops, including cotton. Bt expresses the qualities of the insecticidal gene throughout the growing cycle of the plant. Cotton crops are very susceptible to pest attacks and use up more than 10 per cent of the world's pesticides and over 25 per cent of insecticides.

In India, while cotton is grown on 5 per cent of the total crop area, it uses up 55 per cent of all pesticides. Intensified chemical use has led to a dramatic rise in pest infestation as, over time, they have become resistant to insecticides. Increasing chemical costs and falling cotton prices have pushed thousands of cotton farmers in India, where the majority of the 17 million cotton cultivating families subsist on less than two hectares, into a vortex of debt. Unable to face the consequences of crop failures and mounting debts, thousands of farmers across the country ended their lives in the last five years (Frontline, April 13, 2001).

Given the high chemical dependence of the cotton crop, little wonder that cotton was one of the first crops to be genetically engineered by the US-based agrochemical multinational Monsanto, whose transgenic Bollgard (Bt) cottonseed varieties were a big draw among farmers the world over. Bt cotton, with its promise of reduced insecticide use and resistance to pest attacks - leading consequently to a rise in yields with lower costs - is being pushed by the multinational as an environmentally safe and cost-effective alternative to conventional cotton seeds.

But the Bt toxin targets only the bollworm complex, comprising the American bollworm, the Spotted bollworm, the Spiny bollworm and the Pink Bollworm. The Bt toxin Cry1Ac, approved for commercialisation, is particularly specific to American Bollworm, which attacks the plant after 60 days of sowing. The Pink bollworm attacks the plant after 130 days of sowing - the time of the first pick. While Cry1Ac has only a moderate effect on the Pink bollworm, none of the Mahyco hybrids has any impact on pests such as Thrips, Aphids and Jassids, which attack the plant during its early phase. Thus, while the number of sprays against the bollworm could come down, there may not be a reduction in the use of pesticides against the other pests.

Sign in to Unlock member-only benefits!
  • Bookmark stories to read later.
  • Comment on stories to start conversations.
  • Subscribe to our newsletters.
  • Get notified about discounts and offers to our products.
Sign in


Comments have to be in English, and in full sentences. They cannot be abusive or personal. Please abide to our community guidelines for posting your comment