Powdery mildew isn’t specific to cannabis. However, the fact that fungicidal sprays are prohibited or limited in commercial grows, makes the disease much harder to treat. For this reason, prevention is the best way to deal with powdery mildew, or any mildew, in your cannabis grow.
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How to Identify Powdery Mildew
Powdery mildew is relatively simple to notice. Unsurprisingly, it appears as a white powdery coating. It usually covers the upper sides of leaves but can eventually spread to the entire plant. This powder-like material is actually fungal spores, ready to spread and infect other plants. So, while this is the most prominent symptom, once you notice it, the plant is already in a relatively late stage of infection.
Earlier symptoms include color loss, yellowing, and bright green or yellow spots. These usually begin appearing on older leaves first.
While most powdery mildew symptoms are found on leaves, they may occur on other parts of the plant as well, including petioles and stems.
Powdery Mildew Is a Humidity Disease
Like many other fungal diseases, powdery mildew only develops in high humidity. However, what makes prevention trickier than other molds, is that this disease doesn’t require the presence of water, just high humidity. So, preventing 100% relative humidity isn’t enough, and growers should aim for a lower setpoint. Even short humidity spikes can lead to outbreaks.
On the other hand, this is good news. Powdery mildew can never develop in lower humidity levels, so if you can prevent humidity from spiking, you may be able to completely prevent this disease in your grow.
3 Tips to Prevent Powdery Mildew Through Climate Control
Cannabis is different from other crops. The level of regulation surrounding the materials growers can use in their grow is much stricter. So, without the ability to use common fungicides, growers must put more effort into prevention. Of course, this isn’t just a means to uphold regulations but also to produce cleaner and higher quality buds.
These three methods to prevent powdery mildew are completely clean and organic, using no added materials or chemicals. By utilizing these techniques, you can prevent powdery mildew and a wide variety of common fungal diseases.
Preventing disease through climate control is always better than resorting to additional materials. So you should start with these methods before resorting to sprays or chemicals.
1. Utilize Dehumidifiers
Using dehumidifiers to maintain the ideal humidity in your grow is the most effective way to prevent powdery mildew. High humidity is the main prerequisite for this disease. So, it’s no surprise that the simplest way to prevent it is by removing this basic requirement.
Dehumidifier manufacturers, such as DryGair, have designed and developed unique models specifically for cannabis.
These units are compact and designed to fit in any grow room. But they’re also equipped with powerful water extraction systems and fans to ensure enough dehumidification capacity to keep your plants dry.
2. Introduce Air Circulation
Maintaining low humidity levels in your growing space is critical. However, in a crowded grow room, you’ll notice conditions aren’t equal everywhere. Humidity may be kept low in certain areas but still be high in others, such as between plants.
This is where air circulation comes in handy. Airflow is essential for disease prevention. It moves air between the plants and inside the foliage to disperse pockets of trapped humidity, where molds can develop.
It’s important to note that airflow can be created using several methods. Horizontal fans, vertical fans, etc., move the air in one direction and don’t create cohesion. So while they may help to a degree, they don’t create a uniform climate in the entire space, leading to discrepancies.
Air circulation, on the other hand, is a method that ensures cohesive air movement to create homogeneous conditions everywhere in the grow room. DryGair’s dehumidifiers, for example, come equipped with a patented air circulation system to provide both necessary functions in one unit.
3. Prune and Space Plants Appropriately
Maintaining low relative humidity levels and utilizing air circulation should be enough to prevent powdery mildew in most grows. However, you can take some extra steps to further ensure prevention.
If you’re still suffering from mildew, it’s likely that some plants aren’t enjoying the dry conditions you created with your dehumidifier and airflow. This can happen, especially in cannabis grows, as the plants grow lusher and buds start growing larger and denser. Both of these increase the plants’ ability to trap moisture in which molds can develop.
In this case, you may want to prune your plants or space them out a little more, to let more air through and help disperse moisture.
At the end of the day, preventing powdery mildew is relatively simple once you understand the underlying principle. By providing a large enough dehumidification capacity, incorporating proper air circulation, and ensuring adequate space between plants, you can completely prevent this issue in your grow.