How To Identify and Control Septoria on Cannabis Plants

How To Identify and Control Septoria on Cannabis Plants

Professor DeBacco


Septoria Identification
Septoria leaf spot can cause leaf loss and reduction in photosynthesis and is one of the most common leaf spot pathogens among the hemp leaf spot diseases.
Scout lower leaves and within the inner canopy where leaf wetness and high humidity occur as this is the likely place for the disease to start.
Look for small irregularly shaped spots with bright yellow margins.  Spots expand to about ¼ inch in diameter and appear brown with a prominent yellow halo. 
As spots enlarge, brown areas become more irregular and develop gray to white centers. 
Yellow halos expand outward from spots. 
Entire leaves rapidly become yellow and drop from plants in advanced cases.



Septoria Life Cycle


Septoria Management
When excess moisture or high humidity is available, fungal life cycles are shorter, and larger numbers of spores are produced. So this can increase the chance of disease later in a plants life cycle when the plants are more dense. During rainy summers, disease can spread rapidly through fields.

Septoria species can overwinter in fields on infected plant debris as pycnidia.
Under cool conditions with low relative humidity, pycnidia may remain viable for up to 9 months in debris.
In contrast, pycnidial survival decreases dramatically in hot weather or when buried in soil (i.e. tilling), to less than one month.


Although alternative hosts have not been identified for the Septoria species that causes leaf spot in hemp, it is likely that weeds or another similar “green bridge” is responsible for survival from one growing season to the next.




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