Causes of Plant Diseases

Plant disease-causing organisms are divided into four groups - viruses, bacteria, fungi and           nematodes. Viruses are very simple forms of life. They are often spread to healthy plants by        insects or on one's hands during normal gardening practices.                                                   

 

Bacterial cells are much larger than virus particles, but they are still too small to see with the naked eye. Bacterial cells move in the water film on the leaf surface or in the water surrounding plant roots or soil particles. They are most often spread by splashing water.

 

Disease triangle

The "Disease Triangle" is a central concept of plant pathology. It is based on the principle that disease is the result of an interaction between a host, a potential pathogen, and the environment. If any one of these factors is missing then disease will not occur.

from the University of Nebraska-Lincoln Department of Plant Pathology