Biotic stress is stress that occurs as a result of damage done to plants by other living organisms, such as bacteria, viruses, fungi, parasites, harmful insects, and weeds. It is a major focus of agricultural research, due to the vast economic losses caused by biotic stress to cash crops. The relationship between biotic stress and plant yield affects economic decisions as well as practical development. The impact of biotic injury on crop yield impacts population dynamics, plant-stressor convolution, and ecosystem nutrient cycling (Peterson and Higley 2001). Biotic stress causes serious losses in the yield and quality of crops, and its control is therefore very important. The use of fungicides and insecticides is limited in crop plants because of their cost and considerations of safety to humans and the environment.