Insect pests are one of the major constraints to increase food production and higher agricultural productivity. On a global level, pests are reported to destroy a significant part of the agricultural harvest. A comprehensive study (Oerke et al. 1999) showed that crop losses due to insect-pests range from 25% to over 50%, depending on the crop and agroclimatic conditions. About five million tons of pesticides are used annually in agriculture world-wide and there is ample evidence to show that pesticide use can often aggravate rather than reduce the pest damage in many crops.