Like disease, insects are important causal factors of biotic stress in crop plants. Insects attack all the crop plants and lead to considerable losses in yield as well as quality. Insect attack leads to various types of damages. In crop plants such as 1) Reduction in plant growth or stunting, 2) Damage of vegetative and reproductive parts, 3) Premature defoliation, and 4) Wilting of plants. Insect cause 14% estimated yield loss of all important crops on global bases. Insect cause yield loss directly either by sucking cell sap or by eating away various plant parts. Insects also cause yield loss through transmission of various diseases.