An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively.
Insecticides are used in agriculture, medicine, industry, and general home use. The use of insecticides is believed to be one of the major factors behind the increase in agricultural productivity in the 20th century.
Nearly all insecticides have the potential to significantly alter ecosystems; many are toxic to humans; and others are concentrated in the food chain.