Common Cannabis Pests and Diseases

Common Cannabis Pests and Diseases

Dec 12th 2023

Cannabis is a versatile plant that can live and thrive in various climates. Not just among humans, cannabis plants are popular among birds, squirrels, moles, and even smaller pests and insects that target both indoor and outdoor growing environments. They can be vulnerable to common diseases and pests, looking for a field feast.

Pests and diseases can weaken cannabis plants and affect their growth. So, the first step in protecting your marijuana plants is to identify their enemies, whether you are growing cannabis indoors or outdoors.

In this guide, we will look at the most common cannabis pests and diseases and discover what you should do to combat them. Let's dive into the details!

Most Common Cannabis Pests

Pests like aphids, spider mites, fungus gnats, leaf miners, and other pest mites are top predators of cannabis plants. These pests can damage indoor and outdoor growers, resulting in less yield and poor plant health. Here's the list of common pests’ cannabis growers may face and ways to eliminate them.


Cannabis aphids pose a severe challenge for both indoor and outdoor cannabis growers. They are usually found on the underside of stems and leaves and come in multiple sizes depending on their age. Aphids are oval-shaped, and some have wings.

The Cotton aphid, the Green Peach aphid, the Potato aphid, the Rice root aphid, and the Cannabis aphid are among the major aphid species that affect cannabis cultivation. If left unchecked, these pests can cause substantial damage to crop, such as distorted leaves, stunted growth, and the spread of viral diseases.


  • Move an infested plant outside so you can spray it and reduce the population.
  • Spray insecticidal soaps and neem oil to minimize aphid activity.
  • Cut off the leaves and buds that are highly infected.


Thrips are sap-sucking and pathogen-carrying pests that can be highly problematic for cannabis plants. They are tiny and fast-moving winged insects with the potential to cause persistent harm to crop by puncturing plant cells. They restrict plant growth and leave white, patchy scrapes on leaves and flowers, which can die if not treated quickly.


  • Insecticidal soaps, Spinosad, neem oil, predatory mites, and beneficial nematodes are effective agents that can be used to combat thrips.

Leaf Miners

Leaf miners are tiny pests that lay their eggs in the tissues of cannabis leaves. They leave irregular, bright trails on leaves that can be easily spotted. The larvae eat leaves from inside, significantly damaging the foliage. Consequently, the plant's ability to generate energy and photosynthesize is compromised, which leads to reduced yields and weakened plants.


  • Spinosad and neem oil are effective agents to kill leaf miners.
  • Parasitic wasp Diglyphus isaea is also a good solution.
  • Remove the infested leaves if possible or crush the larva with fingers when the trail is visible.


Caterpillars are another common cannabis pest that can eat plant leaves, leaving behind small black droppings. Hemp moth and Beet armyworm are two notorious species of caterpillars that can seriously harm marijuana plants. You may even catch the critters in action, which will help you remove them more easily. Caterpillars reproduce slowly but can cause massive damage due to their voracious appetites. They might defoliate cannabis crops, which weakens their health and vitality.


  • Caterpillar sprays, BT spray, and Spinosad are effective in removing these pests.


Mealybugs are honeydew-generating pests that can be a problem in cannabis plants. These small insects attract ants and form sooty mold, causing leaf yellowing and stunted growth. Mealybugs are found around joints between branches. They have a cotton-like, waxy appearance that makes them easy to spot. Mealybug infestations can affect overall yield, harming cannabis plants.


  • Insecticidal soaps, limonene products, and neem oil are potent chemical agents against mealy bugs.

Spider Mites

Spider mites are the most common and biggest enemy of the cannabis grower. These mites pierce plant cells and remove essential fluids, which causes stippled leaves and a decline in plant health. They look like brown or red colored spots to the naked eye. These tiny pests are notorious for reproducing at explosive rates, due to which they're challenging to control and can overrun cannabis plants.


  • Neem oil, sesame oil, and cinnamon-clove tea are good options to control spider mites.
  • Sulfur is also a widely used chemical. However, it shouldn't be used near pets or humans.
  • You can lessen their population by controlling the heat because they find it difficult to reproduce in colder temperatures.

Fungus Gnats

Fungus gnats are another common small-sized pest that can be a challenge to cannabis plants. They live around the upper soil and lower plant canopy, mainly thriving in moist conditions. They emerge from the soil after hatching from eggs. Soil that contains compost made of wood chips is more prone to fungus gnats. Their larvae eat organic matter and plant roots, which can cause stunted growth and damage to root systems.


  • Treat the topsoil with neem oil.
  • Allow the topsoil to dry out for a few days before watering.

Most Common Cannabis Plant Diseases

In addition to pests, cannabis can suffer from plant diseases such as bacterial infections, fungal diseases, and mold. If you don't treat these diseases, they can weaken the plants, inhibit their growth, and damage the leaves and buds. Here are the most common cannabis diseases that growers may encounter.

Powdery Mildew

Powdery mildew is one of the prevalent diseases affecting a wide range of horticultural and agricultural crops. Also, it is a common disease that cannabis growers face. It attacks young leaves and damages stems, buds, stalks, and leaves before spreading to other garden areas.

Powdery mildew is treatable and reversible if detected early. If not, your cannabis plant will die. The early signs of this disease are the appearance of a white powdery substance on leaves and humps on upper leaf surfaces. It stops photosynthesis, which inhibits growth and harms your entire harvest.


  • Neem oil, dilute potassium bicarbonate spray, and sesame oil can be used to prevent the germination of this fungal disease.

Gray Mold or Botrytis Cinerea

Gray mold, also known as bud rot, is a fungal infection that can infect plants at any stage of their life cycle, including the post-harvest stage. This disease attacks dying or dead tissue and infects damaged parts that result from pruning or pests. Gray mold thrives on wet plant tissue. It looks like a white powdery substance before turning into a fuzzy, grayish-smoky color.


  • Neem oil, potassium bicarbonate, compost tea, and sesame oil are useful remedies.
  • Sanitize all gardening tools and equipment.
  • Follow proper sanitation procedures and avoid cross-contamination with uninfected plants.

Fusarium Wilt

Fusarium wilt is caused by Fusarium fungus that can seriously harm a garden. The fungus is found in soil, and it can survive in it for years. The disease is evident on cannabis leaves as small, dark blotches that turn yellow brown. After that, leaf tips curl up and remain that way on the plant. Fusarium also causes root rot that begins under the soil, where it attacks the roots and then moves up toward the plant stem.


  • Compost tea and compost are effective antifungal agents.
  • Treat infected soil and seeds.

Mosaic and Leafroll

Cannabis mosaic, also called tobacco mosaic virus (TMV), is a pathogen that causes twisted leaves and unusual mosaic-like mottling patterns of bright colors on leaves. It inhibits plant growth, though it's harmless to humans. Your cannabis plants might seem sickly and grow slowly.


  • Remove infected plants from the garden because once a plant contracts the disease, it can't be cured. There are currently no recognized treatments for this disease in cannabis plants.

Final Thoughts

The best approach is to take preventive steps and protect your cannabis plants. Remember to clean and sterilize your gardening tools and growing space. Monitor your plants and remove any dead or infected plants from your garden. You may use nets or screens to stop insects from entering your farm or garden. Growing cannabis from good-quality seeds rather than clones is another way to avoid infestations. So, follow basic preventive measures, optimize the grow room conditions, and enjoy a healthy harvest!

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