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.