Powdery mildew on plants – combat strategies for cannabis

Powdery mildew on tomato plant leaves

Hey there, fellow cannabis grower! We know how passionate you are about cultivating healthy plants, which is why we’re here to help you tackle a common problem: powdery mildew. In this guide, we’ll walk you through everything you need to know about dealing with powdery mildew on your precious cannabis plants. By the end, you’ll feel empowered to protect your green beauties and maintain a thriving garden. Let’s dive right in!

Disclaimer: Any information given on this site is for educational purposes only. Please ensure if you’re growing cannabis, you’re doing so in accordance with the law and subject to appropriate permissions and licences of the applicable country.

What is Powdery Mildew?

Alright, let’s start by getting familiar with powdery mildew. Picture this: a white, powdery coating that can plague your cannabis leaves, stems, and buds. Not the kind of guest we want in our grow space, right? Powdery mildew is a fungal disease that thrives in humid conditions with poor air circulation. But fear not, we’re going to equip you with the knowledge to combat it effectively.

What does Powdery Mildew look like?

Spotting early signs of powdery mildew is crucial. Look out for these telltale signs: 

  • Powdery white patches or spots on your leaf surfaces, stems, or buds
  • Stunted or distorted growth
  • Leaves curling or yellowing prematurely 
  • A musty, damp smell

Powdery mildew is harmful, but not fatal to your plants. The sooner you catch it, the sooner you can deal with it!

What causes powdery mildew?

The main causes are high humidity, poor airflow or circulation and an invasion brought in on infected plants or clones. 

Preventing Powdery Mildew

Now, let’s discuss powdery mildew prevention. We’re all about stopping it in its tracks! Here are some practical steps you can take to ensure that your grow space doesn’t have a climate that promotes the growth of powdery fungus. 

Maintain proper air circulation: 

Keep the air flowing in your grow space. Set up fans or an exhaust system to prevent stale air and create a breezy environment that powdery mildew hates.

Optimise humidity levels: 

Aim for a humidity range of 40-60% during the vegetative stage and 40-50% during flowering. Keep an eye on those levels using a trusty hygrometer and use dehumidifiers if necessary. Checkout our resources on the ideal temperature and humidity for your grow tent and grow room.

Provide adequate spacing

Give your plants some breathing room! Overcrowding restricts airflow, making it easier for powdery mildew to spread. So, give ’em space and let them flourish!

Maintain cleanliness: 

Keep your grow area spick and span. Remove any debris that could harbour those sneaky fungal spores. Regularly sanitise your tools, surfaces, and equipment to minimise the risk of contamination.

How to treat powdery mildew on plants

Sometimes, despite our best efforts, powdery mildew can still rear its ugly head. But don’t fret! Here’s how to get rid of powdery mildew on plants:

Act promptly: 

As soon as you spot powdery mildew, spring into action. Isolate and remove affected plants to prevent the fungus from spreading like wildfire.

Prune and discard: 

If your leaves are turning yellow then it’s time to get rid of them! Carefully prune and remove any infected leaves, stems, or buds. Bag the plant debris up tightly and dispose of it properly to avoid further contamination.

Organic remedies to the rescue:

Nature has your back! Consider using organic solutions like neem oil, baking soda solutions, or potassium bicarbonate sprays as a treatment for powdery mildew. Always follow the instructions to ensure safe and effective treatment.

Fine-tune the environment: 

Adjust your grow room conditions to make life difficult for powdery mildew. Lower the humidity, increase airflow, and maintain a steady temperature. Powdery mildew won’t know what hit it!

Use a Grow Sensor:

Introducing the Grow Sensor, your ultimate ally in monitoring and optimising your grow spaces! With this cutting-edge technology, you can effortlessly keep track of your growing environment and soil data from anywhere, at any time. Say goodbye to guesswork and hello to actionable insights that enhance the quality, quantity, and consistency of your precious crops.

The Grow Sensor empowers you to identify and manage microclimates, troubleshoot issues, and prevent nutrient waste and pest problems. With its intuitive desktop and user-friendly mobile apps for Apple and Android devices, the provided insights inform your decision-making process, helping you save costs and ensuring a return on investment. The innovative and reliable hardware, coupled with precision wireless sensor equipment, guarantees fast installation, robust connectivity, and unbeatable accuracy. Get ready to take your growing game to new heights with the Grow Sensor!

Grower using a topical spray to treat powdery mildew

Advanced Strategies and Tips

If you’re up for some advanced techniques, we’ve got you covered! Here are a few additional powdery mildew treatments to take your attack to the next level:

Beneficial insects and biological controls: 

Consider introducing beneficial insects like ladybugs or predatory mites to your garden. These natural warriors feast on powdery mildew and help to fight it. Additionally, explore biological control products that contain beneficial fungi or bacteria known to combat powdery mildew.

Preventive sprays and treatments: 

Stay one step ahead by using preventive sprays to protect your plants from powdery mildew. Some products on the market create a protective barrier on the plant’s surface, making it harder for the fungus to take hold. Remember to follow the instructions carefully to ensure safe and effective application.

Strain selection and resistant varieties: 

When choosing your cannabis strains, opt for varieties known for their resistance to powdery mildew. Some breeders specifically develop strains with enhanced resistance, giving you an extra layer of protection. Research and seek out these strains to minimise the risk of powdery mildew in your garden.


Congratulations, my friend! You’re now armed with the knowledge and strategies to tackle powdery mildew head-on. By understanding its characteristics, identifying the early signs, and implementing preventive measures, you can create an environment where powdery mildew struggles to survive.

Remember as with other plant diseases, a proactive approach is key. Regularly monitor your plants, maintain optimal conditions, and act swiftly at the first sign of powdery mildew symptoms. With your dedication and the tools we’ve provided, your cannabis garden will thrive, free from the clutches of powdery mildew.

Happy growing, and may your plants flourish with vibrant health and abundant buds. You’ve got this, champion cannabis grower!

Frequently Asked Questions (FAQs)

FAQ 1: How does powdery mildew affect plant health?

Powdery mildew can weaken plants by inhibiting photosynthesis and reducing nutrient uptake. It can stunt growth, deform leaves, and impact overall plant health, leading to reduced yields and diminished aesthetics.

FAQ 2: Can powdery mildew be eliminated?

While complete eradication of powdery mildew may be challenging, diligent preventive measures and timely treatments can effectively manage and minimise its impact.

FAQ 3: Are there any natural remedies for powdery mildew?

Yes, several natural remedies can help control powdery mildew, such as milk sprays, baking soda solutions, garlic sprays, and mouthwash sprays. These options provide environmentally friendly alternatives to chemical treatments.

FAQ 4: Can powdery mildew spread to other plants?

Yes, powdery mildew can spread to other susceptible plants through airborne spores, physical contact, or shared gardening tools. Proper hygiene practices, such as removing infected plant material, can help prevent its spread.

FAQ 5: What should I do if preventive measures fail?

If preventive measures fail to fully control powdery mildew, consider using treatments like organic remedies or targeted fungicides. Integrated Pest Management (IPM) practices can help develop a comprehensive approach to managing the disease.

Remember, staying proactive, regularly monitoring your plants, and taking swift action is key to effectively preventing and treating powdery mildew infestations.

Note: This guide offers general information on managing powdery mildew. As growing conditions may vary, we recommend consulting with local experts, fellow growers, or horticulturists for specific guidance tailored to your unique circumstances. Stay informed, stay vigilant, and enjoy a powdery mildew-free growing experience!

Author avatar
Lucy Starley
Co founder at Grow Sensor - the smart grow room monitor. Lover of art, animals, sewing, walking and mushroom hunting. Inbound marketing expert and expert tea drinker. Lucy is currently open for Guest posts.

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