Leaf Septoria vs Calcium Deficiency in Cannabis Plants

Leaf septoria and calcium deficiency are two very common problems when growing cannabis.

Interestingly, many indoor growers, especially beginners, fail to identify the problem because the symptoms mirror other plant problems.

As a result, the problem gets worse and worse.

In this article, we will briefly discuss the differences between leaf septoria vs calcium deficiency in cannabis plants and what solutions there are to fix it.

What Is Leaf Septoria?

Leaf septoria is a common fungal infection that affects plants, including cannabis plants.

Leaf spot, also known as septoria leaf spot or yellow leaf spot, is a fungal infection of plants caused by the septoria lycopersici fungus.

The primary symptoms of this infection are white lesions or spots on cannabis leaves.

What Is Leaf Septoria

If the leaf septoria infection is left untreated, the plant will show the symptoms of chlorosis and necrosis.

Finally, the entire leaf becomes covered by the fungus and ultimately dies.

Fungi belonging to the Septoria genus produce pycnidia and ascomycete. These compounds are known to infect many plant species, including Cucurbitaceae (cucumbers, watermelons, and squash) and Solanaceae (also known as nightshade plants, including edible types like tomatoes, potatoes, eggplant, and bell and chili peppers).

More than 1000 different species of pathogens have been found in the Septoria genus, and each of them infects a unique host.

How to Identify Leaf Septoria

How To Identify Leaf Septoria

To identify leaf septoria, the infected leaves will develop leaf spots with a yellow ring. The older and lower leaves will generally be the first to show symptoms.

If you are living in a tropical or subtropical region, the septoria leaf spot can be a common issue.

It is because of the excess moisture level in the soil and high humidity. These environmental factors are favorable for the fungus to thrive.

Leaf septoria has almost the same types of symptoms as nutrient deficiency.

So, as an indoor grower, you’ll need to be able to diagnose the symptoms of leaf septoria disease versus the symptoms of nutrient deficiency.

Effects of Leaf Septoria on Plants

The effects of leaf septoria on plants can be detrimental if not treated right away.

At first, the spores will not affect the flower or new leaves. If you fail to identify the infection, the entire plant and the surrounding ones will slowly be infected and die.

Later, those yellow leaf spots will become brown. If the grower doesn’t treat the affected leaves, the spots will become black and affect the photosynthesis process.

At this stage, the plant will show symptoms like chlorosis. Chlorosis is a condition that prevents plant leaves from producing sufficient chlorophyll.

The lack of chlorophyll will turn the leaves yellow, pale or yellow-white.

This eventually leaves the plant to fail to grow to its full potential.

It is because the lower parts are close to the soil where these fungi start invading the plant leaves.

How to Treat Leaf Septoria on Cannabis Plants

As is the case with the majority of garden pests and diseases, early detection is critical, especially when confronted with leaf septoria.

Keep an eye on your plants during prolonged periods of warm and humid conditions, as well as in the early part of the flowering stage cycle.

Once the disease has been identified, if your plant has leaf septoria, you can take these steps to help contain and prevent leaf septoria.

Remove Infected Parts of the Plant

To effectively treat leaf septoria, the infected leaves must first be removed.

If detected early enough, the disease can usually be contained by pruning all the infected leaves, especially the lower ones. 

Make sure you throw these infected portions away as they can spread to other plants. 

If the disease has spread upward to your flowers, unfortunately, it may be too late. If you remove the foliage and leaves from the flowering areas, the plant will become too weak and the quality of the buds will suffer.

Increase Air Circulation Around the Plants

Proper air circulation is critical for cannabis plants and plays a key role in pest and disease management.

Increasing air circulation can be as simple as installing an additional fan or spacing your plants apart.

However, if you’re working outdoors, this will be more difficult. Pruning can also provide an excellent way to promote airflow between plants.

By trimming back overgrown portions, leaves won’t be touching or layering on top of one another.

If your plants are outside, you can elevate them slightly to allow for more wind exposure. 

If you’re looking for a pair of shears, we have a list of other pruning shears to consider.

Remove weeds and Adding Mulch

Fungal spores frequently spread from the soil, where they remain dormant until the conditions for germination are favorable. While you cannot change the growing medium you are using in the middle of planting, you can take precautions to prevent spores from the ground from spreading onto your plants.

  • Begin by removing dead foliage, weeds, and any potentially infected vegetation.
  • Thoroughly dry your soil, and do not overwater your plants.
  • Finally, cover your soil with a thick layer of mulch and water your plants. This will help stop the fungal spores from spreading to the leaves of your plants.

Monitor Temperature and Humidity

Bear in mind that leaf septoria occurs naturally in hot, humid conditions.

As a result, if you’re fighting an infection, if at all possible, try lowering the humidity levels with a dehumidifier and cooling the temperature with an air conditioner.

Additionally, to control excess moisture:

  • Avoid watering your plants from above. By watering above, the leaves become wet, making it a good environment for fungus and disease.
  • Don’t water as much to allow the soil to truly dry out more
  • Water early in the day so that the soil can dry out during the day.

Use Fungicides or Essential Oils

In a mild case of leaf septoria, the above suggestions may be sufficient to eradicate the disease and prevent it from spreading.

However, if you have a serious leaf septoria infection, you need to use fungicides.

Generally, a broad-spectrum fungicide spray will usually suffice. Consider using a copper-based fungicide for added protection.

Always follow the instructions carefully when using any type of fungicide and, at all costs, avoid spraying the buds.

A natural alternative is using horticultural oils such as neem. Neem oil is frequently used to treat a variety of plant pests and diseases. It is also very easy to apply as a spray.

Some other essential oils, including cinnamon, eucalyptus, lemon oil, or rosemary oil, can be used.

Keep in mind that these oils have potent compounds and smells, so do not spray them onto your buds to avoid contaminating their flavor or aroma. 

Preventing Future Leaf Septoria Infections

When it comes to growing cannabis, prevention is always preferable to treatment. Below are some tips to prevent and mitigate leaf septoria infections.

  • Rotate your plants: Grow your plants in a different location each year. Fungal spores are extremely resilient and may return to attack your crops if they are grown in the same areas.
  • Change the growing medium: Grow your cannabis plants in a new and fresh growing medium the following year.
  • Clean your grow space: Regularly clean the area so that there are no contaminants that can affect your plants. 
  • Maintain a good environment: If you’re growing indoors, ensure that the temperature and humidity levels in your grow space are appropriate. In addition, make sure your plants have enough airflow.
  • Pruning should occur on a regular basis.

What Is Calcium Deficiency?

As the name suggests, calcium deficiency is the result of a lack of calcium in the plant.

Calcium is one of the most essential nutrients, like nitrogen, phosphorus, potassium, sulfur, and magnesium, that are required for plant growth.

In order to grow at their full potential, cannabis plants require calcium at every stage, from seedling, to harvest, and even the flowering stage.

Calcium improves the strength of the plant stem and structure.

How to Identify Calcium Deficiency?

When the cannabis plant has low calcium content, you will notice bronze or brown spots on the leaves. This is the first symptom that your cannabis will reveal.

Sometimes the leaves become yellowish, but most of the time, the color becomes dark.

If you grow the plants under LEDs, then the spots will look purple. Calcium deficiency is caused mainly by acidic soil or low soil pH.

How To Identify Calcium Deficiency

Calcium deficiency in plants is often hard to identify because the symptoms are slow to surface.

Remember that iron, calcium, and magnesium deficiencies appear together. That’s why it is often hard to diagnose.

First of all, look for the leaves. If you notice that there are yellow-green spots on the leaves, then there will be a chance that your plant lacks calcium.

If this condition prevails, then these spots will become reddish or brown.

If the plant reveals more problems, like stunted growth with distorted and curled tips, then it is clear that the plant needs more calcium.

How to Treat Calcium Deficiency in Cannabis

The best way to deal with this problem is to feed the plants calcium-rich fertilizer, like 1tsp. Tiger Bloom Plus per gallon.

You may add gypsum for supplying calcium quickly. You can also use hard water or normal tap water to flush the plants.

Watering is considered a good option. Moreover, applying liquid fertilizer is also a good choice for adding calcium.

Difference Between Leaf Septoria and Calcium Deficiency

Difference Between Leaf Septoria And Calcium Deficiency

To be honest, it is quite hard to identify the differences between leaf septoria and calcium deficiency.

At the onset of each, both of these problems initially come up with similar symptoms – yellow leaf spots.

However, there are some tests and observations you can make to determine whether your plants are affected by leaf septoria or if they are just calcium deficient.

Below are the things to look out for to help you identify the differences when the problem is first detected.

The Color of the Leaf Spots

Calcium-deficient plants have a yellowish-green color between the veins at the beginning and towards the end of the affected leaf, the color turns reddish-brown. A plant infected by leaf septoria fungi will be tan to brown [1].

Weakness in the Branches

Weakness in the branches will be immediate when calcium availability is low. Cannabis stems and branches become weaker because of the lack of calcium.

On the other hand, the strength of plants affected by the leaf septoria fungus at their beginning stage will not be affected. However, if leaf septoria is left untreated, the entire plant will become weaker.

pH Level of the Soil when the leaf spots first Appear

Finding out the pH level in the soil is an easy detection tool to determine whether you have leaf septoria or if your plant is just calcium deficient.

If your soil has a low pH, then your plant is calcium deficient; if the pH level is normal, then chances are your plant is infected by leaf septoria.

Are the Leaf Spots Only on the Bottom Leaves?

If you find that leaf spots are only located on the bottom leaves, then there is a high chance that you have a leaf septoria infection. This is because the fungus has not spread upward toward the flowers.

Are the Roots of Your Plants Weak?

If you notice leaf spots and your cannabis plants are tipping over, it may mean that your plant has weak roots. Weak roots and leaf spots indicate a calcium deficiency (not leaf septoria).


Is leaf septoria caused by pests?

No, leaf septoria is not caused by pests. Septoria leaf spot is a fungal infection caused by Septoria lycopersici. It is a severe plant disease and is particularly acute in areas with prolonged periods of wet, humid weather. Septoria leaf spot usually starts on the bottom half or lower leaves of the plant, then moves up to the top of the plant as it gets worse.

Can Leaf septoria spread to other plants?

Yes, leaf septoria spread to other plants. Whether by insects, wind, water, or human contact, these spores can absolutely spread to other surrounding plants. As lesions or leaf spots grow in size, the leaves will yellow. The leaves eventually die and fall to the ground, infecting the soil with additional spores. This is the main reason leaf septoria will begin spreading with a plant’s lowest leaves that are closest to the ground.

How Can I Treat a Plant Infected With Leaf Septoria?

There are several things to do when treating a plant infected with leaf septoria. First, remove the infected leaves. Removing any infected portions of the plant will prevent further infection. Next, you can use a fungicide, such as Neem oil, to begin controlling the infection. Other things to do are increase air circulation around the plants because warm humid environments are the perfect breeding ground for the septoria fungus.

Does leaf Septoria affect the Buds?

Leaf septoria is unlikely to affect cannabis buds because it rarely affects portions of the plant such as fruit and flowers. However, if leaf septoria is left unchecked, the disease can decimate a large amount of foliage. This ultimately puts plants under a great deal of stress and limits their development as well as the size and shape of their harvests.

Can Septoria leaf spot be cured?

Yes, leaf septoria can be cured. You will need to be patient though. Make sure you completely cut off infected leaves, provide a dry and cool environment, rotate your plants, and finally apply fungicides to control and get rid of septoria leaf spot disease as soon as you notice the leaf spots.


Growing cannabis in your garden will require you to be vigilant and look out for any leaf spots.

Leaf spots can be caused by leaf septoria or calcium deficiency, so you’ll need to identify which it is.

Leaf septoria can be a real problem if you don’t treat it. The best way to handle this is to remove the infected leaves and apply a fungicide.

Calcium deficiency mainly occurs due to an imbalance in soil reactions. In this case, feed the plants with organic nuts or other fertilizers.

Moreover, the growing medium or the pots can be flushed with calcium-rich water to increase the pH level.

Other Common Cannabis Growing Issues

Besides leaf spots from septoria and calcium deficiencies, there are other common issues that indoor growers face. Read more on our related posts:


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