Insecticides

Insecticides are agricultural chemicals that exterminate insects harmful to plants.

Powerful insecticides do kill the bug, but also take out beneficial insects farmers want to keep around.

Bed nets treated with inexpensive pyrethroid insecticides are the main defense against biting, malaria-carrying mosquitoes, and they have significantly cut down on the number of cases. The World Health Organization reports malaria infected an estimated 212 million people in 2015, killing some 429,000 of them.

Charles Wondji, a mosquito geneticist at the School of Tropical Medicine in Liverpool, England, notes that resistance to pyrethroid insecticides occurred rapidly, in about eight years.

Finally, Maitland worries about the problems with emerging drug resistance, both to the insecticides that are used to treat bed nets, to guard against biting mosquitoes at night, and to the most effective tool in the medical arsenal, artemisinin-based compounds. Resistance to the drug has begun to show up in Cambodia.