Are applied on the surface of plants or are added to the bait. The insecticide is eaten along with the food material by insects that chew such as caterpillars.

Are sprayed or dusted on the insect’s body. The poison is absorbed through the body wall. Most soft-bodied insects are vulnerable to contact insecticides.

Are applied to foliage and they have a long lasting effect as they remain on the surface for a longer time. Insects absorb deadly doses by touching the poisoned surface.

Are absorbed by plant tissues, so that when insects feed on the sap they are controlled.

Are insecticidal gases. Insects that lurk out of reach of sprays are killed when they breathe the gas. In addition, the soil may be fumigated to destroy grubs or wire worms that attack roots.