What Causes White Spots on Cannabis Plants and How to Fix It

White spots on cannabis leaves can be a grower’s nightmare. These seemingly innocent marks can indicate various issues, ranging from insect infestations to fungal diseases. If left untreated, these problems can escalate, affecting the overall health of your plants and, ultimately, your yield. In this comprehensive guide, we’ll explore the common causes of white spots on cannabis leaves and offer solutions, including how AirROS can be a game-changer in preventing white spots caused by fungi and powdery mildew. We’ll also delve into prevention tips and best practices to ensure that your cannabis plants remain healthy and productive.

Common Causes of White Spots

Insect Infestation

One of the most common reasons for white spots is insect infestation. Two bugs that are particularly notorious for this are thrips and spider mites.


Thrips are oblong bugs that live closer to the middle stalks of the plant. They rasp away at the leaves and suck sap. Over time, they can even grow wings, allowing them to fly from plant to plant, thereby increasing the risk of a widespread infestation.

Spider Mites

Spider mites are smaller and best seen through a magnifying glass. They create webs on the leaves, which is a bad sign for your plant’s health. These webs serve as a mode of transportation for the mites, allowing them to spread quickly to other plants.


  • Natural Pesticides: Using natural pesticides like neem oil spray can be an effective first step in combating these pests. Neem oil acts as a repellent and disrupts the life cycle of insects.
  • Soil Change: These bugs also lay eggs in the soil. Changing the soil of infested plants after dealing with the initial infestation can prevent future outbreaks.
  • Natural Predators: Some growers use natural insect predators like ladybugs as an advanced technique to control infestations.

Mold, Mildew, and Fungus

If insects aren’t the culprits, then mold and fungal diseases like powdery mildew, botrytis, and downy mildew might be. These fungi spread by sending their spores into the air around your plants.

Powdery Mildew

This is a common fungal disease that appears as white powdery spots on the leaves. It thrives in humid conditions and can spread rapidly if not controlled.


Also known as “bud rot,” botrytis is a gray mold that can also cause white spots on your cannabis leaves. It’s particularly dangerous because it can infect the buds, leading to significant yield loss.

Downy Mildew

This fungus appears as white spots on the upper side of leaves and a downy growth on the underside. It prefers cool, wet conditions.


  • Quarantine: If you identify a plant with a fungal infection, immediately quarantine it to prevent the spread to other plants.
  • Leaf Removal: Carefully remove and dispose of affected leaves or branches. Make sure to sterilize your cutting tools afterward.
  • Air Purification: Using air purifiers can help remove fungal spores from the air, reducing the risk of infection.

The AirROS Advantage

While traditional methods can be effective, they often require constant vigilance. This is where AirROS comes in. Our system operates at low levels of 30ppb or lower for ozone and 60-90ppb for hydrogen peroxide. These Reactive Oxygen Species (ROS) combine to form trioxidane, which is highly effective in killing pathogens but safe for your plants.

white spots on cannabis leaves

Why Choose AirROS?

  • Safety: AirROS operates at levels that are safe for both plants and humans, meeting OSHA standards.
  • Effectiveness: The combination of ozone and hydrogen peroxide creates trioxidane, a compound highly effective against a wide range of pathogens, including fungi responsible for white spots.
  • Ease of Use: AirROS systems are easy to install and can operate 24/7, providing continuous protection against pathogens.

Prevention Tips

  • Hygiene: Maintaining good hygiene by disinfecting all equipment can go a long way in preventing white spots.
  • Air Circulation: Proper air circulation and ventilation can help in reducing the humidity levels, thereby making the environment less conducive for fungal growth.
  • Humidity and Temperature: Monitoring these two factors can help you create an environment where fungi and pests are less likely to thrive.
  • Fertilizer Usage: Being cautious with fertilizer can prevent soil salt accumulation, which can stress plants and make them more susceptible to diseases.

White spots on cannabis leaves can be a sign of various problems, but identifying the cause early and taking action can help ensure your plants are healthy. AirROS provides a safe and effective solution for preventing white spots caused by fungi and powdery mildew, allowing you to focus more on growing and less on troubleshooting.

Ready to say goodbye to white spots on your cannabis plants? Invest in AirROS today and experience the difference it can make in creating a healthier growing environment.


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