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Powdery Mildew – Part 2

What Is the Powdery Mildew on My Marijuana Plants?

If you have ever attempted to grow marijuana and found a white or gray powdery substance clinging to the plants, this is mildew. Like some other types of fungi, mildew can wreak havoc on the health of a marijuana plant and could prevent healthy bud formation. It is essential growers fully understand what mildew growth is and how they can treat their plants once it occurs.

What Is White Powdery Mildew?

White powdery mildew can occur due to various types of fungi. When the conditions are right, mildew will begin to flourish, leading to significant problems with growth. Unfortunately, mildew is not always easy to spot right away.

Mildew can enter the plant through various means, and it is often not noticeable until it begins to grow in high numbers. Mildew can be transported to marijuana plants in multiple ways, including the following.

  • Your clothing
  • Pets
  • Ventilation system
  • Tools

Unfortunately, mold and mildew spores can attach to a marijuana plant and stay dormant for a long time, waiting for the opportune moment when conditions are prime for growth. Once the spores activate, they will begin to take over the plant quickly.

Why Is Mildew Dangerous to Marijuana Plants?

Powdery mildew is one of the most common problems for marijuana growers. Even the most experienced growers can find themselves dealing with this annoying issue. While this fungus problem may not seem like such a big deal, it can cause issues for marijuana growth and should be avoided if at all possible.

Regrettably, mold spores are always floating around in the air, and they live on almost all surfaces. When they are found in small numbers, they rarely cause any significant problems for marijuana growers. Once they begin to colonize, growers will start to see the white powdery development.

White mildew typically comes from the saprophytic fungus. It is harmless to humans and animals, but it can cause problems with photosynthesis, which is the process whereby plants make energy. If the leaves are completely covered in mildew, they will not be able to absorb energy from the sun adequately.

When a plant cannot perform photosynthesis, it will begin to yellow and become faded. Photosynthesis helps to produce chlorophyll, which gives marijuana plants like green crack and big bud their vibrant green color. This process should never be interrupted, or the plant life will suffer, and buds will not grow in abundance.

How to Recognize the Signs of White Powdery Mildew

It is vital growers can spot the signs of mildew on their autoflowering or feminized marijuana plants. Being able to recognize the problems will allow cultivators to take the steps that are essential for protecting their plants’ growth.

White powdery mildew shows up as white fuzzy spots on the plants. Many people believe this fungus looks like spilled flour. Before the white mildew shows up in abundance, marijuana plants can begin to experience the following signs of trauma.

  • Mottled leaves
  • Yellow spots
  • Pale coloration
  • Mosaic patterns on leaves
  • Wilting and drooping leaves

Before the white powder begins to form, you will notice the fan leaves will begin to develop tiny blisters. If you are not paying great attention, these blisters can sometimes be easily overlooked. There is no mistaking the white powdery mildew. It can form on the leaves and buds and will sometimes grow in the soil.

Should you notice any of the above signs, it is likely white powdery mold is the culprit. It is imperative growers act quickly once they see these changes to their auto strawberry cheese or zkittlez marijuana plants. When the fungus begins to inhabit the plant, it will cause health degradation and eventual death. Although mildew is undoubtedly a concern, there is no reason to panic if you see it on your marijuana plants. We will get to the suggested treatment methods shortly.

What Causes White Powdery Mildew to Develop?

Multiple risk factors can lead to an increase in the chances of mildew development. Understanding the risks can help growers to mitigate them, successfully preventing mold growth from occurring on their plants whether they have come from indoor grown seeds or .

High humidity is the most significant risk factor for the development of white powdery mildew. If the relative humidity rises above 55%, the chances of mildew growth increase exponentially. When a grow room does not have enough ventilation and a high humidity level, this can lead to disaster very quickly.

Another risk factor for the development of white mildew is putting your plants too close together. While there are grow methods that call for growers to place their plants in a tight space, when the plants are too close, air cannot circulate properly. Make sure you plan ahead with the layout of your growing space so place do not end up too crowded once they reach full maturity.

Younger marijuana plants are more vulnerable to mildew because it can take over just about every part of the plant. It is especially critical more immature plants are protected to ensure the conditions are not favorable to mildew growth during the vegetative phase.

How to Get Rid of White Powdery Mildew

Once mildew infiltrates the marijuana plant, it is challenging to remove. If the mildew growth is thick, there may be no hope to save the plant. The best way to stop powdery mildew is to prevent it from growing. If your 3 kings strain marijuana plants are infected with white powdery mildew, taking the following steps may save them, but acting quickly is essential.

  • You will need to mix two tablespoons of organic apple cider vinegar with one quart of water.
  • Put this mixture in a new plastic spray bottle.
  • Spray your plants liberally with the apple cider vinegar mixture.

If caught in time, the apple cider vinegar will not only destroy the existing white powdery mildew, but it will also help to prevent new mildew growth from occurring. There is also an alternative if you do not want to use vinegar.

  • You will need to mix one-half tablespoon of baking soda with one quart of water.
  • Place this mixture inside a new plastic spray bottle.
  • Spray your marijuana plants all over to cover the mildewed leaves.

It is possible to use both of these treatment methods as a preventative. Many growers spray their plants as soon as they enter the vegetative stage. You can also use other natural remedies, including the following.

  • Sesame oil
  • Fish oil
  • Neem
  • Bacillus subtilis
  • Streptomyces lydicus
  • Hydrogen peroxide
  • Milk
  • UVC light exposure
  • Sulfur burners

There are multiple methods for getting rid of mildew, but it takes a concerted effort. It is better to work to prevent it from occurring. If you start preventive measures from the very beginning, it is likely the plants will be able to avoid mold and mildew growth.

Take These Preventative Steps

Prevention is always better than attempting to treat a mildew problem that has developed. If you are growing marijuana, it is imperative the conditions are ideal, and the following preventative steps are taken.

  1. If you purchase clones, do not introduce them to other plants until they are found to be healthy. Lab testing can allow you to be sure the specimens are not contaminated before adding them to a grow room.
  2. It is also imperative you ensure the grow room has the right humidity levels. Carefully monitor the humidity and make adjustments if it goes too high. Remember to try and keep the level around 55% or under, depending on the growth stage.
  3. A forced-air setup can help to prevent mildew growth from invading a grow room.
  4. Make sure there is plenty of air circulation, so too much moisture is kept at bay. By increasing the air circulation, plants are less likely to develop mildew growth.
  5. Another step that should be taken is to make sure you filter the air coming in. The right filtration system filters out both large and small particles and sterilizes the air before it enters the grow room.
  6. Sterilization is critical for the grow room and all equipment and tools. The grow room should be cleaned thoroughly after each harvest before new plants are started. Always begin a new crop with a completely sterilized environment for the best prevention.
  7. It is also critical you control who is allowed to enter the grow room. The more people allowed inside, the higher the chances of mold exposure. It only takes one active spore to populate the plants with powdery mildew. If you allow anyone to enter, they should wear protective gear to cover their street clothes.
  8. Watering plants from above can put them at risk for mildew development. Never water marijuana plants at night because the water will not have time to be evaporated and will sit on the plants for many hours.


Taking care of marijuana plants can sometimes seem like a full-time job, especially when there are pests like mold and mildew to handle. Thankfully, there are preventative strategies that can be put in place.

Using the above information should allow you to prevent mildew growth and understand what to do if that pesky white powder begins to develop. If you notice white powder on your plant’s leaves or stems, simply take the right steps and help your marijuana plants heal from the fungus, allowing them to create big, beautiful buds from your i49 seeds purchase.


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