Pesticides control or kill pests by physically, chemically or biologically interfering with their normal body behavior. Their goal is to eliminate any insects that might eat valuable crops. To be effective , a pesticide needs to be absorbed through the surface of the plane tissue. When a pest, like an insect,slug,snail or mouse starts to nibble on a plant, the pest ingests the chemical and is destroyed .
One common type of pesticide is called a herbicide. Herbicides can be used to clear roadside weeds, trees and brush . They can also kill weeds that may cause environmental damage.