Septoria cannabis is a species of plant pathogen from the Septoria genus that causes Septoria leaf spot. Early symptoms of infection are concentrated on the vegetative leaves of cannabis plants, followed by chlorosis and necrosis of the leaf. Septoria , which is an ascomycete and pycnidia producing fungus, has been known to attack Solanaceae and Cucurbitaceae species as well as many species species. This genus is known to encompass over one thousand species of pathogens, each infecting a specific and unique host.
Hosts and symptoms
This disease only infects cannabis or hemp plants. Symptomatic responses associated with this disease will be in the form of white lesions with concentric rings on the surface of the vegetative leaves, as well as browning and chlorosis on infected leaves.  The first symptoms of this disease will occur on the older, lower leaves of the plant. Septoriahas never been known to grow rapidly and will eventually succeed all of the cannabis’ vegetative growth rendering it unable to perform any biological processes and ultimately die. If the disease is the most vegetative tissue will be destroyed, taking away the cannabis plant’s source of sugars and eventually turning into a sink and reduce yields. Nitrogen deficient cannabis plants are more likely to be infected. Though Septoria destroys vegetative growth it has no impact on the formation of buds. This disease was discovered in New York dating back to 1884, and was recently found in North Carolina. 
The disease cycle for Septoria cannabis is identiques To That of Septoria tritici  or Septoria of tomato  except for the manufacture of a perithecium INSTEAD of a pseudothecium. Being a polycyclic disease, it can asexually produce conidia in a pycnidium which continually inoculates new hosts throughout the growing season, as well as sexually producing ascospores in a perithecium which acts as an overwintering structure. The disease survives on debris from the previous growing season as ascospores in a perithecium, as well as on the epidermal tissue layers of leaves. The thick cell wall of the ascospores provides protection and allows for the rest of the world.  When the conditions are favorable (summer-fall) the spores are released. Once infected the disease quickly spreads via the production of conidia in the secondary cycle which is accompanied by the sexual production of ascospores. Pycnidium are formed on the leaf lesions.
Septoria is present in many parts of the world, but has only become prevalent in the marijuana industry with the movement towards legalization. Ranging from the Emerald Triangle in California, Septoria is becoming an increasing nuisance for cannabis growers. Like most septoria species, they require moist and moist conditions, because of their conidia being immotile, and survive during the off-season.  The disease moves to other parts of the body during the period of rain or heavy wind, which allows the dispersal of ascospores (primary cycle) and conidia (secondary cycle) to roam and infect other vegetative tissue. 
The management associated with Septoria of tomato is very similar to that of Septoria cannabis . To avoid this disease, you must eliminate survival structures that are dead and decaying.  Sanitation of your growing area can make the difference when battling diseases of any nature. Many diseases like Septoria thrive in an area that provides excessive decaying material, by removing dead leaves. Since SeptoriaRaising the number of suitable hosts and increasing the spacing of your cannabis plants  The use of fungicides (Bordeaux Mixture, Gold Daconil 2787)  are also applicable when the disease has infected your plants. Good practices such as avoiding overhead irrigation, especially before dusk, will decrease the amount of stagnant water on your leaves that can trap windblown conidia spores. Eliminating survival structures is one of the most important aspects of disease control in Septoria and can be accomplished by covering or growing debris.
- Fungorum Index
- USDA ARS Fungal Database
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