Diagnosis of Major Disease-causing Pathogens
Many marijuana plant diseases are recognized by characteristic symptoms on host plants. More specific identification of disease may require observations of characteristics of the causative pathogen. Fungi are identified by their spores and fructifications (fruiting bodies), also called spore-bearing structures.
These are examined under the compound microscope directly after removal from the specimen. The specimen should be kept moist for a few days to promote fructification development, or the fungus may be isolated and grown on artificial nutrient media, and identification made on the basis of fructification produced on the media.
The shape, size, color, and manner of arrangement of spores on the fruiting bodies, as well as the shape, color, orientation, etc. of the fruiting bodies, are sufficient characteristics to suggest, to one somewhat experienced in taxonomy of fungi, the identity of the particular fungus pathogen.
Bacteria can be isolated from leaf spots and blights by surface sterilizing the area to be cut with sodium hypochlorite (Clorox), removing a small part of the infected tissue with a sterile scalpel, and placing it in a sterile plate containing a nutrient medium.