March 29, 2017

Powdery Mildew on Marijuana Plants

March 29, 2017
Powdery mildew can harm beautiful cannabis plants.

The road to a successful cannabis harvest is fraught with potential roadblocks, potholes, and if cannabis cultivation is prohibited in your area, traffic stops. Numerous problems can (and will) occur until those trichomes are milky and amber. Aside from improper lighting, fertilizer, pruning, and watering, various types of fungi can plague your fertile pot palace. Powdery mildew is but one concerning fungal example, yet it can be effectively treated. 

What Causes White Powdery Mildew on Plants?

If you’re unsure what causes powdery mildew on plants, there are several possible origins. Humidity above 55% and poor ventilation create the ideal environment for spores to develop and flourish. Powdery mildew is difficult to detect before it starts growing, and it can make contact with your plants in a variety of ways. With an outdoor grow, white powdery mildew spores may travel through the wind; alternately, they could fly into an indoor grow room through the ventilation system. Spores can also be transported by pets, people, clothing, and/or gardening tools. 

What Are the Symptoms of Powdery Mildew?

What does powdery mildew look like? Powdery mildew manifests as fuzzy white spots on leaves resembling flour. The white fungus on plants may cause the leaves to wilt and get mottled in appearance while the fungus spreads quickly throughout the plant. White powdery on pot plant leaves will destroy other plant parts as well, so it’s very important to stop the mildew from spreading as soon as possible. 

What Conditions Does Powdery Mildew Like?

Powdery mildew thrives in a moderate temperature range (68-86°F) with minimal light and ventilation. Humidity is also an important factor, which is why I recommend keeping humidity above 55%. Many cultivators discover powdery mildew weed in greenhouse settings because those conditions are ideal for spore growth. 

Will Powdery Mildew Affect My Buds?

If you have powdery mildew on plants, it can affect the plant’s buds. Without treatment, white powdery mold anywhere on your marijuana plants will eventually spread, producing powdery mildew on buds. Once this marijuana mold takes hold of your buds, they won’t be fit for consumption. Nobody wants a moldy toke! 

Does Powdery Mildew Contaminate Soil?

Powdery mildew cannabis isn’t your only concern, as this cannabis mold can also contaminate soil by growing within it. While difficult to detect without a microscope and specific microbiological knowledge, cannabis cultivators can take measures to protect their soil from these fungal parasites. That said, small amounts of powdery mildew in soil won’t necessarily doom your entire crop. 

Is Powdery Mildew Harmful to Humans?

Only those with serious mold allergies may be vulnerable to powdery mildew health risks. Although mold on weed doesn’t pose a direct threat to humans, it can provoke a serious reaction in those who are allergic. If you’re not allergic to mold, powdery mildew weed won’t hurt you if you touch it, but it can be harmful to your cannabis plants, significantly reducing their harvest yield. 

Can Powdery Mildew Be Washed Off?

The crucial question is: how to get rid of powdery mildew? Powdery mildew can be washed off during all cannabis plant growth stages, but this can be a meticulous task requiring significant labor resources. More importantly, washing off powdery mildew marijuana isn’t near as difficult as preventing the mildew’s spread. 

Will Powdery Mildew Go Away?

Unfortunately, powdery mildew won’t go away without proper treatment and spread prevention. There are several methods and substances that can be used to treat the mold, but preventing its spread is key. Once powdery mildew emerges in your cannabis plants, it must be treated or removed.

How Do I Treat Powdery Mildew?

There are several ways to treat powdery mildew. You can use a mixture with 1/2 teaspoon of baking soda and 1 quart of water. Spraying sesame oil or fish oil onto affected plants will work similarly. Other types of oil sprays are less commonly used but can also be effective. These sprays include clove, cottonseed, cinnamon, garlic, and coriander oils. Some cultivators claim a simple mixture of 2 parts milk and 3 parts water will also effectively remove powdery mildew. 

How Do I Get Rid of Powdery Mildew after Harvest?

Discovering powdery mildew after harvest is nothing less than catastrophic, which is why powdery mildew prevention is key. If you have mildew on your marijuana plant’s buds after harvest, you’ll likely have to destroy the crop because the buds may pose health risks related to allergies. Do your best to remove all infected plants to prevent further spread, and hopefully you’ll be left with some healthy buds. 

How Long Does It Take to Get Rid of Powdery Mildew?

The time required to get rid of powdery mildew depends on methods used, the extent of the infection, and the size of your cultivation operation. Applying treatment and waiting for results could take about 48 hours, while removing rampant infection from a large crop could take 2-3 days. 

What Is the Best Fungicide for Powdery Mildew?

Most cannabis consumers today are looking for their weed to be grown in a fungicide-free environment, which necessitates using organic powdery mildew fungicides. You can utilize beneficial fungi such as gliocladium and trichoderma or Bacillus subtilis, a soil-dwelling bacteria with fungicidal properties. Copper is an important micronutrient for cannabis cultivation in general, and its inclusion in soil will provide an organic powdery mildew treatment as well. 

Does Hydrogen Peroxide Kill Powdery Mildew?

While hydrogen peroxide isn’t necessarily a powdery mildew cure, it can kill this mold and won’t be harmful to your marijuana plants. I would suggest purchasing a mixture with 3% hydrogen peroxide concentration from your local supermarket or drugstore. Gently spray affected areas of your plants as well as the soil with a hydrogen peroxide/water mixture. 

Does Vinegar Kill Powdery Mildew?

Vinegar can be effectively used as a powdery mildew spray. Start with this remedy: 2 teaspoons of organic apple cider vinegar mixed with 1 quart of water. Put this mixture into a spray bottle, and spray the infected areas of your marijuana plants. This will likely kill the mildew and prevent any future spores from developing on your plants.

Will Dish Soap Kill Powdery Mildew?

Utilizing a proper mixture of dish soap, baking soda, and water can kill powdery mildew. Combine one tablespoon of baking soda, one-half teaspoon of dish soap, and one gallon of water, then spray the mixture liberally on affected areas of your plants. 

Additional Readings on Cultivation

The Weed Blog is a comprehensive source to find reviews of specific top strains of cannabis and online news resources regarding the legalization of marijuana. We are committed to helping you find valuable information about cannabis on our website. With marijuana law constantly changing, learn about the latest legislation from our website and what you can do to help. Otherwise, consider these other top tier articles regarding cannabis cultivation:

Bud Rot and Your Marijuana Plants

How to Kill Spider Mites on Your Marijuana Plants

Cannabis and Humidity 101: The Fundamentals of Grow Room Humidity Control


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