Friday, May 7, 1999 Published at 02:40 GMT 03:40 UK
GM pests bite back
Genetically-modified food: The row continues
By Helen Briggs of BBC Science
Genetically modifying crops to protect them against pests may not work, according to research published in Science Journal.
Insect damage to crops like maize costs farmers billions of dollars a year.
It is one of the arguments for planting crops that have been modified to produce an insecticide capable of killing the pests that feed on them.
But this latest research, carried out at Kansas State University, is likely to fuel the debate over GM crops.
Immunity through exposure
The researchers found that insects can become immune to insecticide through over-exposure, in the same way that bacteria, responsible for human diseases, can become resistant when exposed to too many antibiotics.
The report confirms that corn borers, which attack maize, develop immunity to insecticide much more quickly than was previously thought.
And this could spread rapidly as the insects breed.
So far these experiments have only been carried out in the laboratory.
But if the same results are seen in cornfields, it means scientists may have to think again about how to protect crops from attacks by pests.