Your cannabis plants can get affected by various types of diseases, but imagine waking up one day to find powdery stuff sprinkled on your cannabis leaves. It's even more awful if it's on the buds.
If you're a beginner, you'll wonder what caused it. Could it be the resin the buds produce? Nah, the resin is sticky.
What about trichomes? Could the trichomes be producing something? The questions keep coming.
However, if you're an experienced cannabis grower, you'll immediately realize that your plant is affected by powdery mildew. It's an infection that affects a wide range of plants and cannabis is no exception. Caused by several fungi species, it can make your cannabis plants look like they are covered in talcum powder.
The term "powdery" refers to the white powdery patches that form on plant parts like leaves, stems, and buds.
In this article, we will explore everything you need to know about powdery mildew and what you should do if your plants are infected. Let's begin!
Understanding Powdery Mildew
Powdery mildew is an infection that affects many plants. It flourishes in warm and dry environments, posing major challenges in cannabis growing facilities where humidity levels may be high.
The fungus manifests as a white or grayish layer on leaf surfaces, stems, and other plant parts. It predominantly impacts the upper leaf surface, but it can sometimes develop on the undersides as well.
Severe infestations can result in leaves yellowing and the leaves can die very early, ultimately decreasing the plant's strength and yield.
The fungus mainly targets the cells of the plant, creating a layer that disrupts photosynthesis and nutrient absorption. If not treated promptly, powdery mildew can have an impact on plant health, development, and productivity.
Addressing powdery mildew is crucial in cultivation, whether you're growing cannabis in a small closet at home or have a huge commercial operation, due to its prevalence and harmful impact on plant health and yield. This fungus can spread rapidly among crops if you don't control it immediately.
For commercial cultivators, powdery mildew poses a huge threat as they can face large financial losses. Nobody wants to smoke moldy buds, and you won't even go back to the dispensary that sold them in the first place, would you?
Infected plants may suffer from stunted growth that eventually leads to reduced yields. Most importantly, the buds will have reduced cannabinoid levels, so you won't even get what you expect from them.
Moreover, the presence of powdery mildew jeopardizes the safety of other cannabis plants as well, so you need to take it very seriously.
And, it's not dangerous just for the plants. Contaminated plants could contain pathogens and toxins which can be a threat to human health as well. Thus, the faster you get rid of it, the better.
Life Cycle of Powdery Mildew
Powdery mildew's life cycle is dynamic and is largely influenced by the health of the plant and other environmental factors. Although it's not necessary to understand the life cycles to get rid of the disease, it can help you gain a better understanding of how it can affect your plants.
1. Spore Germination
Powdery mildew spores, called conidia, are transported by air or when water is splashed on the plant's surface. When the conditions are favorable, like temperatures (around 70-80°F or 21-27°C) with high humidity, these spores start to germinate. Germination initiates with germ tubes forming and they eventually elongate to develop into structures known as appressoria.
2. Colonization
Once the germ tubes produce appressoria they enter the plant's cells through structures called haustoria. Haustoria functions as feeding organs that enable the fungus to draw nutrients from the host plant. The fungus spreads across the plant's surface creating a white to gray powdery growth.
3. Reproduction
As the fungus colonizes the plant, it begins generating spores (conidia) on plant parts surfaces. Clusters of conidia are produced in chains, giving the appearance of a powdery covering. These tiny spores can easily travel through the air, water, or human movement, facilitating the spread of the fungus among plants.
4. Dormancy
On the other hand, when the conditions aren't very favorable, the fungus enters dormancy and slows down. Consequently, its ability to reproduce stops. As a survival strategy, the fungus may create special structures containing the spores so it can endure unfavorable conditions for extended periods. Once the environment is favorable again with high humidity and moderate temperatures, the fungus can quickly resume its growth and reproductive processes.
As you can see, powdery mildew relies on cues from the environment and the physiology of the plant host to thrive. Thus, one approach is to target the stages of its cycle to disrupt growth and limit disease spread.
Causes of Powdery Mildew
Powdery mildew is influenced by a mix of factors, including plant health issues and genetic predispositions.
1. Environmental Factors
When warm temperatures combine with humidity, it provides the perfect environment for powdery mildew to thrive. The fungus particularly flourishes in temperatures between 70-80°F (21-27°C) and with extreme humidity levels above 60-70%. Additionally, stagnant air worsens the situation by aiding the fungus in spreading.
To reduce the risk of powdery mildew due to humidity, you can install dehumidifiers to maintain proper moisture levels. In addition, if your grow room or tent has inadequate airflow, it can lead to air pockets raising the chances of powdery mildew outbreaks. Thus, make sure there’s adequate airflow for moisture dissipation and preventing the infection from spreading further.
If your grow tent has a very dense canopy, you can trim back foliage to enhance airflow and lower moisture in the canopy.
2. Light Intensity
Extremely intense light can create hot pockets of air within the canopy and create the perfect conditions for powdery mildew growth. To prevent this, ensure there’s a proper light distribution across the canopy to reduce such hot spots. Again, you can trim your plants to reduce the likelihood of such problems.
3. Overcrowding
A dense canopy with too many plants crowded together can promote powdery mildew development too. And when such conditions are paired with limited airflow and low light in cramped areas, it can create environments for powdery mildew to flourish. Plants in the canopy receiving light and airflow are especially prone to infections.
4. Plant Stress
Stressed plants are more susceptible to powdery mildew infections. Various stressors like deficiencies, improper watering methods and environmental fluctuations such as temperature or humidity changes can weaken plants. Nutrient deficiencies, especially a lack of nitrogen, can compromise the plant's system making it more vulnerable to fungal attacks.
Remember, small things like watering also matter. If you water much more than the plant requires, it can lead to root rot and other moisture-related issues that harm plant health. On the flip side, plants that are not watered enough may also undergo stress, making them more prone to powdery mildew. When plants lack water, they struggle to stay healthy and are targets for fungal infections.
Cannabis plants can also get stressed when there are sudden fluctuations in the environment around them. For instance, if there’s a sudden rise or drop in the temps, the plants will get affected.
5. Genetic Predisposition
Certain cannabis varieties are naturally more prone to powdery mildew due to various factors. Specific genetic characteristics can make plants more susceptible or less capable of defending against fungi. On the other hand, some varieties show resistance or tolerance to powdery mildew. For this reason, it may help to choose varieties that have the ability to resist powdery mildew.
Impact of Powdery Mildew on Cannabis Plants
Powdery mildew infestations can greatly affect cultivation by influencing plant growth, yield, economic viability, and harvest quality. Here are a few ways as to how it can affect plants:
1. Impeded Growth
Powdery mildew hinders photosynthesis by covering leaf surfaces with mycelium which blocks sunlight absorption. This obstruction in photosynthesis results in less energy for growth, so the plants struggle to develop properly. As a result, you will notice stunted growth, and the plant may not grow as much as other plants of the same age, lowering the potential yield.
2. Decreased Flower Production
As the plants become stunted, they will not be able to produce buds. The buds will either be very small or won't form at all as powdery mildew directly affects flower development.
You may also notice that the buds on infected plants may be smaller and less dense with reduced levels of cannabinoids and potency.
3. Premature Senescence
Premature senescence is nothing but the plants aging faster than normal. It occurs when severe powdery mildew infections speed up the aging process of cannabis plants causing leaves to yellow, wither, and drop prematurely due to stress from the fungus. This premature leaf drop reduces the plant's ability to conduct photosynthesis and produce energy, so the plant will not grow as much and produce less yield as well.
4. Cannabinoid Levels
The presence of powdery mildew may lead to a reduction in the levels of cannabinoids found in cannabis plants, such as THC and CBD. If you're a commercial producer, you'll understand how important cannabinoid levels are for users, regardless of whether they are using it for recreational or medicinal purposes. Cannabis users purchase it mainly for the properties of cannabinoids, so powdery mildew can be detrimental to you.
On the other hand, even if you're a grower, you'll also be impacted by powdery mildew as you won’t like using weed that's low in cannabinoids.
5. Reduction in Terpenes
The terpene profile which gives cannabis its flavors and scents might decrease in infected plants. This can lead to an odd taste and smell in the final product. Or, there may be no smell at all.
6. Safety issues
Concerns about safety arise with powdery mildew as infected plants could contain pathogens or toxins that could jeopardize your health. Some growers try to smoke buds affected by powdery mildew but it's very risky. It can affect your respiratory system and create many issues.
How to Identify Powdery Mildew on Cannabis Plants?
Identifying powdery mildew on cannabis plants is crucial for implementing control measures and stopping the spread of this disease.
Here are some signs you should watch out for:
1. White Powdery Growth
The main indication of powdery mildew is the presence of a powdery substance on leaves, stems, and buds. Initially, small white spots may appear on the plant, which then develops all over the plant. This is an early sign of infection. Later, this powdery substance can completely cover leaf surfaces and quickly spread across the plant in humid conditions. When you touch it, leaves or other parts of plants that are affected may leave a powdery substance on your hands or fingers.
2. Leaf Damage
When leaves are infected, they show signs of harm such as turning yellow, browning, or tissue death (necrosis).
As the infection advances, leaves might start to curl, twist, or change shape. Leaves that are severely affected may dry up and die early resulting in a loss of foliage.
3. Stunted Growth and Less Yields
Powdery mildew hampers photosynthesis by covering leaf surfaces, which reduces the plant's ability to produce energy. As mentioned earlier, you'll see that the plants are stunted and struggle to grow as they can't generate energy for their growth and development. As a result, the plant will not be able to produce buds properly, resulting in decreased yields.
4. Musty Smell
As the infection progresses, powdery mildew can give off a mildew-like smell. You will notice it when examining infected plants up close in enclosed growing areas.
5. Webbing or Dense Fungal Mats
At times, powdery mildew might create web-like structures or thick fungal mats on buds and leaves, indicating the infection has progressed to an advanced stage with excessive fungal spores that spread and make matters worse.
6. Visible Fungal Features
When you look at the spores through a magnifying glass, you'll see fungal spores that could be gray or white in color. Powdery mildew has the potential to quickly spread to other leaves, stems, and buds. To prevent this, you should regularly inspect your plants for powdery white substances so it doesn’t spread throughout the plant and your entire cultivation space.
Detecting these indications at an early stage helps you manage powdery mildew effectively.
How to Prevent Powdery Mildew From Infecting Cannabis Plants?
Preventing powdery mildew is crucial to keeping your cannabis plants healthy and maximizing your yields. We have already discussed some of the points we have mentioned below; however, we will reiterate them again so they are all in one place and you can go through them at once. Here's how you can protect your plants from powdery mildew:
1. Start with Healthy Plants
Begin by choosing healthy seeds or clones that are free from all types of diseases. You can do this by purchasing from good breeders or getting clones from nurseries you trust to avoid introducing powdery mildew to other plants in your grow tent. Be sure to inspect the plants before making a purchase.
2. Optimize Growing Conditions
Maintain daytime temperatures between 68-77°F (20-25°C), although it can be slightly cooler at night.
Use a hygrometer to monitor humidity and keep the RH between 40 to 60% consistently. Lower humidity levels with a dehumidifier if necessary.
Ensure consistent airflow by using fans or ventilation systems to prevent air pockets. Using oscillating fans can enhance airflow within the growing area.
3. Provide Adequate Spacing
Avoid overcrowding plants to allow enough airflow between them. Proper spacing also aids in preventing the spread of powdery mildew. If the canopy is much too dense, prune branches and foliage to improve airflow and penetration throughout the canopy.
4. Maintain Cleanliness
Maintain a nice and clean growing environment to stave off powdery mildew. Promptly remove any plant debris or dead material that could harbor fungal spores.
In addition, regularly sanitize tools, equipment, and growing areas to curb the spread of spores. Disinfect your tools every time you use them to prevent your new plants from getting affected.
Regularly sanitize your tools, pots, and surfaces to stop the spread of germs. Mix one part bleach with nine parts water and spray it on all surfaces inside the grow room. This way, if there’s an infection already, it won’t spread to new plants you grow.
5. Opt for Resilient Plant Varieties
Select cannabis strains that are naturally resistant to powdery mildew. Look for varieties bred specifically to resist diseases as breeders put in a lot of effort to choose disease-resistant varieties and crossbreed them to create strains that inherit the best features of their parent plants. Some popular resilient cultivars include Blue Dream, Northern Lights, and White Rhino.
6. Take Preventative Actions
They say that prevention is better than cure, so you can practice the same to prevent powdery mildew too. Rather than waiting for an infection to take hold of your plant, try to prevent it by using various remedies to shield plants from powdery mildew.
To start off, you can use concentrated cold-pressed neem oil. Make sure you dilute it according to the manufacturer’s instructions and spray it on leaves to prevent fungal infections.
Next, you can use sulfur-based products and administer them on the plants very early during their vegetative stage to deter powdery mildew.
Combine 1 tablespoon of baking soda with 1 gallon of water and a few drops of soap. Spray this mixture on plants to alkalize leaf surfaces and deter powdery mildew from spreading further.
Mix 1-2 teaspoons of potassium bicarbonate per gallon of water and spray it on plants including the undersides of the leaves. This method disrupts the cell walls of the fungus, halting its growth.
You can also introduce bacteria such as Bacillus subtilis into the soil. Follow the instructions of the manufacturer to mix it in water and spray it on the leaves to enhance plant immunity.
Finally, you can also use milk. Yes, milk! Many growers don't know about this but you can combine one part milk with nine parts water and spritz it on plants to prevent powdery mildew. The lactoferrin in milk acts as a fungicide.
7. Watering Practices
Try to water the plants properly from below. This means that you should only water the soil rather than the leaves. Some growers pour water on the plants; however, moist foliage can make problems worse and invite powdery mildew. Instead, opt for drip irrigation so the plants get water at timely intervals in a proper manner.
Also, the timing matters. Water your plants in the morning so that the leaves have time to dry out before nightfall, which helps lower the chances of infections. If growing indoors, water when the lights are off but switch the fans on so the soil dries out a bit.
8. Monitor the Plants
Regularly check your plants for any signs of powdery mildew like white powdery spots on the leaves and stems. Take action promptly at the sign of infection to stop it from spreading to plants. Inspect your plants thoroughly, paying attention to the undersides of leaves where powdery mildew commonly begins.
9. Use Natural Pest Control Methods
Bring in insects such as ladybugs or predatory mites that prey on powdery mildew and other pests.
Apply fungicides that contain mycoparasites or Trichoderma to prevent powdery mildew from spreading. Remember to switch between various fungicides with varying modes of action regularly to prevent the fungi from developing resistance. Alternate between chemical and natural fungicides to prevent them from becoming immune to treatment.
11. Keep Your Plants Healthy
Make sure your plants are getting enough nutrients but don't overdo it as plants can also get stressed by nutrient burn or over-fertilization, making them more vulnerable to powdery mildew. Make sure you do everything to keep the plants as healthy as possible. For example, regularly check the pH levels and adjust them as needed for optimal nutrient absorption.
12. Isolate New Plants
Before introducing new plants into the grow tent, isolate them for a minimum of two weeks so they don't bring any pests or diseases with them. Keep an eye on the plants for powdery mildew before adding them to your garden.
By following these steps you can lower the chances of powdery mildew affecting your cannabis garden and enjoy the benefits of having healthy plants all season long.
How to Get Rid of Powdery Mildew on Cannabis Plants?
Sometimes, there's a possibility of the plants getting affected despite taking all sorts of preventive measures. In such cases, keep these things in mind to get rid of powdery mildew as fast as possible.
1. Isolate Affected Plants
Immediately separate plants displaying signs of powdery mildew to stop it from spreading the disease to other healthy plants. Place the infected in another quarantine area with proper airflow to prevent the spread of the disease.
2. Get Rid of the Affected Plants
Collect all the infected plants, leaves, buds, and other parts and get rid of them. Thoroughly sanitize your tools so they don't spread the disease to other plants. Clean your tools after each cut to prevent contamination. For example, you leave open wounds on the plants when you prune the leaves, leaving them vulnerable to infections. Apart from that, if the plant is infected already, using the same tool on another plant can spread the disease to that plant as well.
At this point, you can use baking soda or neem oil and spray it on the plants to prevent the infection from spreading out of control.
If the infection persists, apply fungicides to manage powdery mildew. As mentioned earlier, use sulfur-based fungicides following the instructions on the label to eliminate powdery mildew spores.
Similarly, you can use copper-based fungicides to protect plants from further damage.
Summary: The Effects Of Powdery Mildew On Cannabis Plants: How To Prevent And Eliminate It
Powdery Mildew is a fungal disease that can affect many plants. Similarly, cannabis can also become vulnerable to this disease and succumb to its effects. There are various ways to prevent this disease from spreading further as it’s best to prevent it rather than trying to eliminate it once it has damaged the plants.
Powdery Mildew can affect the yields significantly, so you need to keep an eye out on the plants and check for any white powdery residue or spots. Ignoring the problem will only help it spread throughout the plant and reduce yields drastically. Thus, take action immediately!
