Washington, June 8 : A new research by scientists has found that genetically modified (GM) plants that use a common soil bacterium to kill pests, won't harm beneficial bugs that are the natural enemies of the pests.
Entomologists at the Cornell University in the US conducted the research.
The research showed that GM plants expressing Bt (Bacillus thuringiensis) insecticidal proteins are not toxic to a parasite that lives inside the caterpillar of the diamondback moth, a devastating worldwide vegetable pest.
"The conservation of parasites is important for enhancing natural biocontrol that will help suppress pest populations as well as reduce the potential for the pest insects to develop resistance to the Bt," explained Anthony Shelton, Cornell professor of entomology at the New York State Agricultural Experiment Station in Geneva, NY, who conducted the study with postdoctoral associate Mao Chen.
The Bt bacterium, which is not harmful to humans, has been used for decades as a leaf spray and since 1996, in GM plants, a method that has proven much more effective and is now more widely used.
Both uses are approved by the US Environmental Protection Agency.
"Few studies have examined the effect of Bt plants on parasites of caterpillars, but some of them have reported negative impacts," said Chen, noting that the new research suggests that those negative findings were likely due to testing methods.
To separate out the effect of insecticides and Bt proteins on the caterpillar and parasite, the Cornell researchers isolated and bred strains of caterpillars that were resistant to Bt or a conventional or organic insecticide.
Then, the caterpillars were parasitized with a wasp that kills the caterpillar in nature.
The resistant caterpillars were then either fed GM plants expressing the Bt protein or non-GM plants sprayed with the Bt protein, conventional insecticides or organic insecticides.
The parasitized caterpillars that ate plants treated with conventional and organic insecticides to which they were resistant, survived and developed into moths because the parasite was killed by the insecticide the caterpillar ingested.
However, when the caterpillar fed on the Bt-sprayed plants or Bt plants, the parasite was not affected and killed its host caterpillar when it emerged as an adult wasp, showing that Bt plants are not toxic to the parasite.