Infectious diseases are caused by living organisms called pathogens. Noninfectious diseases caused by environmental stress and damage by weather and other environmental factors. Environmental factors that cause a plant to be stressed may result in the plant’s gradual decline. Decline results in the plant being more susceptible to disease organisms. There are at least 50,000 diseases of crop plants. New diseases are discovered every year. About 25% of the total world’s crop production is lost annually to infectious diseases despite improved cultivars and disease control techniques. Damage from disease has not been eliminated. Disease-causing organisms pathogens multiply and mutate rapidly. They develop genetic resistance to chemical controls and have the ability to infect new hybrids. This session discusses more about infectious diseases in plants.