Fungi

Bacteria Bacterial diseases can occur within houseplants and greenhouse-grown varieties, but are more common in outdoor plants. This is partly due to the fact that many types of bacteria that infect plants are often transmitted by insects that create a wound in the plant, allowing the bacteria to get inside. Several types of parasites like whiteflies, scale and aphids can act as carriers of the bacteria, which is transmitted to the plant when the insects feed on it. Bacteria can also be transmitted by pruning equipment shared between infected and non-infected plants.
A two-pronged approach to bacterial prevention would include include controlling the parasites with a natural insecticide like AzaGuard. Plant wounds can be treated for bacteria using a foliar spray like OxiDate (for food crops) or ZeroTol (for ornamentals). These organic chemistries can be tank-mixed for ease of application.
Viruses Viruses, like bacterial infections, require an opening in the plant through which the virus can get past the cell’s rigid cell wall. Humans can transmit plant viruses via grafting and parasites can also act as carriers of the virus. Unlike bacteria, viruses actually infiltrate the plant’s cells, and then replicate themselves to create more infected cells. Since the virus lives inside the plant’s cells, there is no way of removing a virus without destroying the plant cells in the process, making chemical treatments futile.
Normally plant viruses only cause a loss of crop yield. Therefore it is not economically viable to try to control them, the exception being when they infect perennial species such as fruit trees.