Chris DeWildt

November 12, 2018 3 min read
November 12, 2018
3 min read

Growers Network’s Disease Profile: Septoria Leaf Spot

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In this series of articles, Growers Network talks about a few of the most common Cannabis diseases you need to watch out for. Today’s topic: Septoria leaf spot.

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Plant diseases are a major headache in any grow operation and Cannabis has no shortage of diseases that would love to ruin your crop. So for today’s profile we’re going to discuss Septoria Leaf Spot, a disease you may find yourself dealing with in your grow.

Quick Look

  1. Common Name: Septoria Leaf Spot/Yellow Leaf Spot/Leaf Spot
  2. Scientific Name: Septoria cannabis
  3. Symptoms: White-yellow lesions on leaves, browning of leaves, chlorosis (whitening)
  4. Caused by: Fungus
  5. Timing: Summer-Fall (spores can survive in detritus year-round)

Septoria Leaf Spot

The fungus Septoria cannabis causes Septoria Leaf Spot. (photo courtesy of

What is Septoria Leaf Spot ?

Septoria leaf spot, also called “Yellow Leaf Spot” or just “Leaf Spot” is a fungal disease with various species that infect a wide variety of plants. The Septoria cannabis species however is limited to infecting hemp and Cannabis only. As seen above, it is characterized by causing yellow-white circular spots to appear on the leaves. Left untreated it will spread to all vegetative growth, leaving the plant unable to complete biological processes. While not often fatal, this disease will result in slowed growth and low yields.

What to look for

As previously mentioned, Septoria symptoms include leaf spots, leaf death, and chlorosis (whitening of the plant). Conditions that invite this disease include wet leaves, dead plant material in the vicinity, and humidity.

How to Prevent/Treat Septoria Leaf Spot

Non-Chemical Control

To prevent Septoria Leaf Spot it’s important to control the environment of the grow. Here are a few prevention tips:

  1. Keep relative humidity low.
  2. Make sure to clean up and remove all dead plant material as these can host fungal spores and reinfect when the time is right (Summer-Fall).
  3. Avoid overhead watering if possible, especially in the evening as wet leaves can facilitate infection.
  4. Create additional space between plants to prevent transmission and an all-out infestation of the crop.
Chemical Treatment

There are a variety of commercial fungicides available to combat Septoria Leaf Spot, however, some growers prefer a more biological approach since Cannabis is a consumable product. Before purchasing any chemical treatment, be sure to check the pesticide laws in your jurisdiction, and always follow the product instructions provided by the manufacturer.

So now you know a bit about Septoria and what you can do to prevent it from ruining your grow. Have additional questions about Septoria Leaf Spot? You should join our forum where you can post pics and ask our expert community about this topic or any other!

Happy Growing!

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About the Author

Chris DeWildt is a graduate of Grand Valley State University and Western Kentucky University. He worked in education and publishing for ten years before joining the team at Growers Network.