Pennsylvania State University biologists said their insecticide might be more lethal to crop pests than either ingredient used alone. The "one-two punch" it delivers also reduces the insects' chance of developing resistance, the researchers said.

"We found a synergistic effect, where the two insecticides together decreased the growth rate of caterpillars more than either one did alone," said Professor Dawn Luthe. "The insect mortality rate was also much greater than the sum of mortality rates when only one insecticide was used."

The researchers said their findings have important implications for agriculture since nearly 20 percent of major crops worldwide are annually lost to insects.

Luthe, Mississippi State University Professor Peter Ma and researchers Srinidhi Mohan and W. Paul Williams report their findings in the online journal PLoS One.