Yellow Spots On Cannabis Leaves: How To Deal With Leaf Septoria

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leaf septoria cannabis
Author avatar By Derek LaRose
October 05, 2022
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Are you growing a marijuana plant and seeing brown or yellow spots on the cannabis leaves? Your crop may be suffering from Leaf Septoria, one of the most common and severe issues when growing cannabis.

Perhaps you’re a novice or an experienced grower and want to learn more? Understanding the problem of yellow spots on leaves is essential in marijuana cultivation.

Read on to discover everything you need to know about this harmful disease. We explain how to prevent, recognize, and how to treat leaf septoria.

Let’s sort it out!

What is cannabis leaf septoria and how to identify it?

Septoria leaf spot in cannabis is a fungal disease that attacks many plants, usually appearing as yellow spots on the blades. It frequently occurs in warm, moist conditions. If untreated, it causes massive damage to cannabis crops. So it’s best to spot and treat cannabis leaf septoria early.

There are some telltale signs your weed plant is suffering from the disease. Let’s explore how to detect cannabis with septoria.

leaf septoria

Signs of leaf septoria on cannabis plants

Yellow leaf spots are the primary indicator you may be dealing with a septoria infection. They often appear as circular dots with brown edges, sometimes with a gray color in the center.

The spots start on the lower leaves at the base of the plant. As the infection develops, the discoloration spreads to the upper foliage. If brown dots are more prevalent than yellow, it means the disease is maturing and needs urgent attention.

If you see brown or yellow spots on marijuana leaves, something is wrong, and septoria fungi are likely the cause. To learn more about how to differentiate leaf septoria from nutrient deficiencies, read our “leaf septoria vs calcium deficiency“.

How do septoria leaf spots spread?

Septoria fungi spores love the moisture and heat involved in various aspects of growing cannabis. The leaf spots they cause spread out in multiple ways and can ruin an entire crop.

Water allows the spores to survive and spread throughout the soil. They quickly reach the plant through the root system or by splashing the leaves.

Innocent insects can carry the infection from one cultivar to another, spreading yellow spots on cannabis leaves.

The microbial spores also spread across multiple plants through the air, infecting whole crops. Immediate leaf septoria treatment is required if you think your plants show signs of disease.

How to treat yellow spots on weed leaves

If your marijuana leaves have yellow spots and you’ve established the plant is infected with septoria, don’t panic! It’s possible to cure it. 

Follow our guide to resolve septoria in cannabis.

remove infected leaves

Remove affected cannabis leaves

The first step in saving your weed plant involves removing the affected leaves to stop the infection from spreading

Cutting away the damaged vegetation also refocuses the plant’s energy supply to the healthy leaves, maximizing recovery. Removing sick foliage is a step toward curing leaf septoria in weed but is also universally essential to successful weed cultivation.

Remove some surrounding vegetation in case spores have spread further. Don’t chop off too much at once. Doing so can damage and shock your plant. 

Trimming or pruning cannabis helps the plant in various ways, and it’s essential for fixing yellow spots on weed leaves. Take note of some golden rules when clipping:

  • Ensure the area is clean and free of contaminants
  • Wash your hands or wear gloves
  • Use sharp gardening clippers and avoid serrated blades
  • Never tear away bits with your bare hands
how to treat leaf septoria

Ensure good air circulation

Good air ventilation is essential for marijuana cultivation and dealing with diseases and pests. Circulating fresh air helps to remove spores from the plant. Yellow spots on weed leaves stop appearing as the bacteria dissipates.

Improving air ventilation when growing indoors is simple. Create space between the plants and introduce more fans.

Outdoors can be tricky as you don’t control the environment. If possible, raise the plant to catch higher winds and remove foliage to increase airflow around the plant.

Keep water out of the weed leaves

It’s vital to avoid moisture when managing cannabis leaves with septoria. The fungal disease thrives in damp conditions.

Avoid wetting or splashing the leaves when watering weed plants infected with septoria. Water below them at the beginning of your light cycle so the soil dries out.

Keep the soil clean

Cleaning the soil helps stop the spread of fungal spores. Remove any dead leaves and rake the top layer to eradicate surface contaminants.

Adding mulch can also prevent spores from spreading. Apply a thick layer across the surface of your soil, then water the plant. 

Soil composition significantly affects most aspects of weed cultivation, from disease prevention to bud quality. Using the best cannabis nutrients to boost your plants is a no-brainer.

Use natural oils or fungicides

The final step in curing leaf septoria in cannabis is applying natural oils or fungicides to stop the spread of spores

We suggest avoiding strong products as they can damage the buds. Natural pesticides like neem oil or homemade fungicide are ideal for added protection.

With this final process, the spread of spores and the disease can stop, and the plant heals.

Can I prevent leaf septoria on weed leaves and plants?

Now you know how to get rid of septoria leaf spot, it’s time to learn preventative methods.

Stopping disease and pests from infecting your marijuana plants is easier than removing them. It’s best to take pre-emptive measures to avoid these issues.

Maintaining the correct humidity for cannabis is important but has greater significance when learning how to treat septoria leaf spots. 

When growing indoors, lowering humidity levels is possible as you create the environment. Various methods exist, such as using intake and extractor fans to recycle air.

In extreme cases where cannabis leaves with septoria spots are dying, introducing a dehumidifier may be necessary.

Outdoor cultivators are at the mercy of mother nature. Humidity is outside your control.

Other ways to strengthen your weed plant’s resilience to disease and pests outdoors exist. The condition of the soil is among many elements you can influence.

Give your plants the best chance of a fruitful harvest in natural conditions by investing in premium outdoor weed seeds

Time to leave

Do you think your plant might be suffering from leaf septoria? You know how to prevent, detect, and save cannabis if it occurs. Take this knowledge and continue cultivating, or start as a well-prepared novice. 

Check out the Homegrown Cannabis Co. store to see our incredible range of high-quality products. Find everything from the best autoflower and feminized strains to premium indoor weed seeds.

Growing should be fun, not stressful. Pick your favorite strain, stick to our advice, and look forward to a harvest of healthy and delicious buds.


About the author: Derek LaRose

Also known as Kronic from The Cannabis Kronicles, Derek LaRose is a young ambitious cultivator and a staple educator for indoor cultivation.