There are many different types of insecticides on the market today. Most of our common insecticides have broad-spectrum activity; they are effective against many different types of plant pests. A few insecticides are selective; control is aimed at only one type or group of insects. Insecticides use different methods to control insects. Most insecticides are either systemic or kill on contact. A systemic insecticide is a chemical that is absorbed by the roots, stems, or leaves and is carried with the sap throughout the plant. Any type of pest that feeds on sap from the treated plant is killed. Systemic insecticides usually remain active in the plant for at least 2 weeks, protecting the plant from reinfestations. They are applied either as granules to the soil or as sprays or drenches. Nonsystemic chemicals may control the insect by direct contact (the spray is absorbed through the body) or through ingestion, as the insect feeds on plant tissue. The persistence of an insecticide determines how quickly it breaks down in the environment. The persistence of most nonsystemic insecticides ranges from several days to months. The less persistent the insecticide, the shorter the time interval between applications.
Related Links
Applying Pesticides
Mixing and Storing Pesticides
