The following is an excerpt.
Since 1996, farmers worldwide have planted more than a billion acres (400 million hectares) of genetically modified corn and cotton that produce insecticidal proteins from the bacterium Bacillus thuringiensis, or Bt for short. Bt proteins, used for decades in sprays by organic farmers, kill some devastating pests but are considered environmentally friendly and harmless to people. However, some scientists feared that widespread use of these proteins in genetically modified crops would spur rapid evolution of resistance in pests.
Read the full story here: Biotech Crops Vs. Pests: Successes and Failures from the First Billion Acres
