Vol-27 No.-2, December 2010 J Micro.pmd

Introduction The competition for crops between human and insects is as old as agriculture. The use of chemical substances to control pests was started in the mid-1800s. In past, certain inorganic and organic compounds, including organochlorides, organophosphates, carbamatespyrethroids and formamides were used as insecticides. Because of the special properties of these chemicals, such as long residual action and toxicity to a wide spectrum of organisms, they have been being used for a long time. However, using such chemicals may cause many environmental problems; for example, insect resistance, toxicity to humans, and to beneficial insects1.