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Plant diseases are diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). [1] Organisms that cause infectious disease include fungi , oomycetes , bacteria , viruses , viroids , virus -like organisms, phytoplasmas , protozoa , nematodes and parasitic plants . [ 2 ]
Epidemiology is the study of factors affecting the outbreak and spread of infectious diseases. [10] A disease triangle describes the basic factors required for plant diseases. These are the host plant, the pathogen, and the environment. Any one of these can be modified to control a disease. [11]
Pathogens can spread through the air, water, or on insect and animal vectors (hosts). Dutch elm disease was spread by elm bark beetles, yet the tree mortality was caused by a pathogen. [4] Chestnut blight is a fungus spread through wind dispersal and rain splatter; the blight traveled up to 50 miles in a year by natural means. [5]
Plants can show many signs or physical evidence of fungal, viral or bacterial infections. This can range from rusts or molds to not showing anything at all when a pathogen invades the plant (occurs in some viral diseases in plants). [9] Symptoms which are visible effects of diseases on the plant consist of changes in color, shape or function. [9]
Few varieties are resistant to the disease and none are immune, so rotating susceptible plants with non-susceptible ones like cereals is a practice positive to limiting soft rot infection. The control of specific insect vectors is also a good way of controlling disease spread in the field and in storage.
Although conidia can be spread by rain, the most common means of spread is through the air. [4] The fungus grows on epidermal leaf wax of plants, particularly those in the Brassicaceae , and prefers an environment with high humidity and temperature range of 20–30 °C (68–86 °F). [ 3 ]
Fusarium wilt (Panama disease) is the most serious disease of banana, threatening 80% of the world's banana production, most of which is planted with the susceptible Cavendish varieties. Bananas are a staple food in the diet of millions throughout the subtropics and tropics, and the spread of Panama disease could have devastating effects on ...
Protozoan infections are responsible for diseases that affect many different types of organisms, including plants, animals, and some marine life. Many of the most prevalent and deadly human diseases are caused by a protozoan infection, including African sleeping sickness , amoebic dysentery , and malaria .