Kill only the older mosquitoes

That's the key to stopping the spread of malaria, according to entomological researchers.

"Most mosquitoes do not live long enough to transmit the disease. To stop malaria, we only need to kill the old mosquitoes."

Theoretically, when you kill the younger ones, you introduce selection pressures in favor of pesticide-resistant variants.

Once malaria parasites infect a mosquito, they need at least 10 to 14 days -- or two to six cycles of egg production -- to mature and migrate to the insect's salivary glands. From there they can pass into humans when a mosquito bites.

"We are working on a fungal pesticide that kills mosquitoes late in life," said Thomas. "We could spray it onto walls or onto treated materials such as bed nets, from where the mosquito would get infected by the fungal spores." The fungi take 10 to 12 days to kill the insects. This achieves the benefit of killing the old, dangerous mosquitoes, while dramatically reducing the selection for the evolution of resistance, Thomas explained.