Fungal cannabis diseases

Viral cannabis diseases

Death to diseases


Are there such things as cannabis diseases? You might be surprised to discover that marijuana plants can have various infections. From fungi to viruses, weed crops can contract many diseases.

It’s important to know if your crops are contaminated with pathogens to avoid lower yields and reduced quality. Continue reading to discover what diseases your plants can develop and their signs and symptoms.


Fungal cannabis diseases

Cannabis fungal infections are no laughing matter. From powdery mildew to bud and root rot, these diseases are common in weed plants. However, some fungi can be helpful, mycorrhizae is a good example.

These pathogens may seem scary, but we’ve got the lowdown on cannabis disease identification and simple treatment and prevention methods below. These tips will help you learn how to revive a dead or sick weed plant.

Let’s look at the most common fungal diseases.




fusarium: common cannabis stem problem


Fusarium is known as root rot on cannabis. This pathogen infects the soil where your weed plant grows, resulting in the root rotting.


Signs and symptoms

  • Brown areas on roots
  • Sunken lesions close to the soil line
  • Wilted leaves



Fusarium on cannabis is generally treated using ozone water. This solution cures root rot on weed plants by enriching them with oxygen, destroying the fungus.


a cannabis plant affected from a disease and dying




grey mold: a sick weed plant


Botrytis is the result of bud rot or gray mold. It can remain dormant for long periods of time before flaring up and spreading to other crops. It’s the most common humidity-related disease that weed plants are infected by.

Lack of humidity control increases the likelihood of Botrytis. Since cannabis crops have large amounts of humidity, they’re susceptible to bud rot. You may not notice the infection initially, but there are ways to identify it.


Signs and symptoms

  • Soft buds that have changed color, later turning brown and crisp
  • Sunken, discolored patches on the main stem or branching point



You can treat Botrytis by using ozone water treatment. Oxygenated H2O given to the crops kills off the fungus and saves your buds. Identifying and treating Botrytis prevents you from having a dying weed plant on your hands.


bud rot or grey mold on cannabis: a typical fungal infection


Powdery mildew

You may have a sick weed plant if you see powdery mildew on your marijuana leaves. The fancy name for this disease is Golovinomyces. The symptoms typically only show after a few weeks, and it spreads quickly.

Cannabis powdery mildew is typically caused by too much humidity or moisture. Always ensure that you keep your weed plants in the best conditions possible.


Signs and symptoms

  • Powdery mildew spores on the leaves and buds
  • Brown leaves, which eventually fall off
  • Stunted plants
  • Poor quality buds



Treatment for powdery mildew includes preventative sprays like biopesticides. Make sure you spray your plant ahead of time before the mold has a chance to grow.

This mold spreads easily and quickly, so you need to take action as soon as possible. You can easily use these preventative measures, but remember that sometimes cannabis leaf diseases are inevitable.


powdery mildew on cannabis leaves: a fungal infection


Leaf septoria

In most cases, leaf septoria won’t spread onto the flowers of your weed plant. The fungus attacks the leaves, causing them to wilt and fall off, much like other marijuana diseases.

Leaf septoria generally appears in the early blooming stages. The signs flare up from the bottom to the top of the plant. Like other fungi, this disease thrives in moist and humid environments.


Signs and symptoms

  • Yellow and brown spots on the upper and lower sides of the leaves
  • Generally appears in the flowering stage of the plant
  • Shows on the lower leaves first



Remove the infected foliage as soon as possible to prevent the cannabis leaf disease from spreading further. The next step is to improve air circulation. Avoid moisture and high humidity.

Use fungicides or natural oils to kill and remove the infection. If you want to go the extra mile, use a copper-based fungicide.


cannabis leaf septoria: yellow spots on leaves



Alternaria is one of the more well-known pathogens. It’s a common allergen for humans that causes hay fever and the like. Alternaria is also a weed plant disease.

Like some fungus diseases, you can’t see Alternaria with the naked eye. You’ll only notice it once the symptoms begin to show.


Signs and symptoms

  • Leaf necrosis (gray or black color on the leaves)
    • These spots are light and dark brown
    • They often dissolve and cause holes in the leaves



Proper water and humidity levels help prevent this fungus. If it’s too late for preventative measures, you can use broad-spectrum fungicides to eliminate this cannabis disease.


Verticillium wilt

Verticillium wilt targets plants that have poor drainage. It affects the soil, spreading from the crop’s stem to the leaves. It also occurs when there are too many rich nutrients in the growing medium.

The fungi remain in the soil and attack the roots. They infiltrate the transport system within the radicles, causing several issues.


Signs and symptoms

  • Leaves turn gray and die
  • Stem turns brown at the base



Treat this fungus using proper compost, sterilized soil, and ensuring the ground has adequate drainage. Check that you’re using the best organic nutrients.

Remove any infected plants to prevent the fungus from spreading. Make sure not to spread the spores in the soil.


Verticillium wilt on cannabis: fungal infection


Viral cannabis diseases

Cannabis plant problems aren’t only caused by fungus and mold cultures. Viruses are also a significant factor. Just as humans can get sick, so can your precious weed plant.

While fungi travel via spores and are considered alive, viruses spread by replicating or cloning. Below are some pathogens that your weed crops can contract.


Tobacco mosaic virus (TMV)

The tobacco mosaic virus affects over 100 plant species, including marijuana. Infected crops typically appear sick and grow slower than usual. You’ll likely find leaf problems on your cannabis plants.


Signs and symptoms

  • Pale mosaic or mottled markings on the leaves
  • Twisted growth



This marijuana disease is rare, and there are no known treatments available. Infected plants are sick indefinitely and need to be safely disposed of. Burning is the best way to get rid of ill crops.


TMV on cannabis as a disease


Beet curly top virus

Beet curly top virus, also known as curly top beet leafhopper, is one of the many hemp diseases. Scientists have found that this virus mainly targets hemp plants. It spreads by beet leafhopper insects that carry this nasty virus.

Symptoms are mild initially, but as time goes on, they become much more intense. Some plants, however, can outgrow this virus.


Signs and symptoms

  • Yellowing and molting at the base of the leaves
  • Pale yellow plants
  • Leaves curl upwards
  • Stunted plants
  • New growth will be twisted



Beet curly top virus has always been challenging to prevent for cultivators due to how quickly the insects travel. Insecticides dont work, but certain mulches do.


Beet curly top virus on cannabis


Cannabis cryptic virus

You might be confused as to why the word “cryptic” appears in the name of this virus. It’s no mistake; this pathogen only shows up in the presence of other viruses.

It adds or alters viral symptoms and is transmitted through seeds, so be smart about where you buy weed seeds.

Signs and symptoms

  • Heightened symptoms of hop latent virus
  • Heightened symptoms of lettuce chlorosis virus


The treatment for this strange cannabis virus is the same as for other pathogens. Use insecticides and mulches, or burn the plant to prevent further contamination.


stages of Cannabis cryptic virus on cannabis


Death to diseases

All in all, there are quite a few cannabis plant diseases that you can find on your marijuana crops. Follow our tips and tricks to identify, treat, and prevent these fungal and viral weed diseases.

Find more information on cultivating cannabis on our blog, and don’t forget to browse our store for premium marijuana seeds.

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