An insecticide is a chemical substance designed to kill insects. Farmers spray insecticides on crops to protect them from beetles, aphids, and other bugs that would otherwise devour plants before harvest. Gardeners might use insecticides to save their tomato plants from caterpillars, and homeowners use them to eliminate ants, mosquitoes, or termites.

While insecticides solve real problems by protecting food supplies and controlling disease-carrying mosquitoes, they must be used carefully. Some insecticides harm helpful insects like bees and butterflies along with the harmful ones, and some can make people or animals sick if used incorrectly.

Scientists continually work to develop more targeted insecticides that kill only specific pest insects without affecting other creatures. Some farmers now use insecticides made from plants or bacteria, and others use integrated pest management, combining different methods to control insects while using fewer chemicals. Understanding how insecticides work helps people make smart choices about when and how to use them.