An
insecticide is a substance used to kill
insects. They include ovicides and
larvicides used against insect
eggs and
larvae, respectively. Insecticides are used in
agriculture,
medicine,
industry and by consumers. Insecticides are claimed to be a major factor behind the increase in agricultural 20th century's productivity. Nearly all insecticides have the potential to significantly alter ecosystems; many are toxic to humans; some concentrate along the food chain.