The researchers fed insects a sub-lethal dose of the two insecticides to test the effectiveness of both insecticides on the pests.
They found that when used alone, a concentration of Bt at five parts per billion killed four percent of all corn earworms and five per cent of tobacco budworms. Mir1-CP, when used at a concentration of 60 parts per billion, killed eight percent of the corn earworms and three percent of the tobacco budworms.
But when researchers added the two insecticides together, the mixture killed 61 per cent of corn earworms and 57 percent of tobacco budworms, which is more than 10 times better than either by itself. Researchers saw similar results against the fall armyworm and the southwest corn borer, when the insecticides were used at slightly different strengths.
In addition to a high mortality rate among the insects, the study indicates a significant decrease in the growth rate of the survivors.
"We think that Mir1-CP is making holes in the membrane, which in turn is making it easier for the Bt toxins to reach the insects' midgut," explained Luthe, whose work is funded by the National Science Foundation.
The Penn State researcher says the findings have important implications for agriculture because each year insects cause major losses to farmers. Nearly 20 per cent of major crops worldwide are lost to insects.
Genetically modified crops that produce the Bt toxin have managed to check the insects to some extent but Luthe says insects may be winning the fight.
"Researchers in the Mississippi delta have found resistance to Bt among some insect populations in the region," Luthe noted. "There is a chance that some time in the future Bt will not be as effective against pests as it is now."
The Penn State researcher suggests strains of corn that naturally produce Mir1-Cp could be cross-bred with other strains of corn that
|Contact: Amitabh Avasthi|