ABSTRACT
A general definition of plant diseases is that they are disturbances that affect the normal function of a plant. These disturbances commonly are divided into nonparasitic diseases and parasitic diseases. Nutrient deficiency, cracking of fruits, damage from salinity, air pollution, repeated mechanical injuries, and unfavorable light or temperature are examples of nonparasitic diseases. Parasitic diseases are infectious and are caused by organisms or by viruses. Infection is the successful penetration and establishment of a disease-causing factor in a host plant. Control of diseases involves many procedures, grouped into activities that involve selecting disease-resistant plants, using cultural practices to increase or maintain plant resistance, keeping the causal organisms away from plants, and using pesticides. Changing of crops on a plot of land can help to reduce disease infestation. Fungicides help to protect plants by providing a protective barrier to prevent infection, by killing spores or germinated spores, or by killing the disease after infection.
