General Overview

Viruses are small submicroscopic particles whereas phytoplasmas are much larger and resemble bacterial cells without a cell wall or distinct nucleus. Both require a living host and cause similar disease symptoms which include: a general dwarfing of the plant, lack of proper chlorophyll production resulting in a mottled appearance on foliage, yellowing and in some cases rings on leaves or fruit as well as necrotic (dead) areas. Symptoms may mimic those caused by 2,4-D damage or other disease organisms or even environmental problems. The disease can be spread by feeding insects or mites, or mechanically through hands and tools. If a plant is diagnosed with a virus, the only method for controlling the infected plant is to remove it. There are many cultivars of plants that have been bred to be resistant to certain, more common viruses. 

Specific Diseases