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A wilt disease is any number of diseases that affect the vascular system of plants. Attacks by fungi , bacteria , and nematodes can cause rapid killing of plants, large tree branches or even entire trees.
In small plants and seedlings, Verticillium can quickly kill the plant while in larger, more developed plants the severity can vary. Some times only one side of the plant will appear infected because once in the vascular tissues, the disease migrates mostly upward and not as much radially in the stem. [3]
Fusarium wilt is a common vascular wilt fungal disease, exhibiting symptoms similar to Verticillium wilt. This disease has been investigated extensively since the early years of this century. The pathogen that causes Fusarium wilt is Fusarium oxysporum (F. oxysporum). [1] The species is further divided into formae speciales based on host plant.
A table beet infected with Pectobacterium carotovorum subsp. betavasculorum.Note the rings of black vascular tissue colonized by the rotting bacteria. Beet vascular necrosis and rot is a soft rot disease caused by the bacterium Pectobacterium carotovorum subsp. betavasculorum, which has also been known as Pectobacterium betavasculorum and Erwinia carotovora subsp. betavasculorum. [1]
Flaccidity and chlorosis start in the lower regions of the plant and progressively move upwards causing wilt of the entire plant. [6] In later stages of disease development, progressive defoliation occurs, which is followed by necrosis in leaves. Discoloration of the vascular system is a characteristic symptom.
Botanists define vascular plants by three primary characteristics: Vascular plants have vascular tissues which distribute resources through the plant. Two kinds of vascular tissue occur in plants: xylem and phloem. Phloem and xylem are closely associated with one another and are typically located immediately adjacent to each other in the plant.
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 ]
Plant disease triangle. 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]