How to prevent bud rot for cannabis GMP certification

Bud rot is, in fact, the same fungal disease as botrytis or gray mold. But when it comes to cannabis, as the dense buds create the perfect conditions for it to develop, it’s known simply as bud rot. It’s also one of the most common issues in cannabis cultivation, leading to large amounts of yield loss and ultimately losses for growers.

Needless to say, greenhouses and grow rooms that suffer from bud rot don’t comply with GAP and GMP requirements. So they won’t be able to produce cannabis for medical, or even recreational purposes in most cases. Today Ziv Shaked with DryGair talks to us about how to prevent bud rot. 

Cannabis greenhouse with DryGair dehumidifiers 

Bud rot symptoms
Bud rot develops when the botrytis cinerea fungus infiltrates the plant and begins to develop. The first apparent signs usually show up on or around the infected buds in the form of dark or soft spots. In later stages, it breaks out as a gray fuzz.

"But by the time the first symptoms appear, the plant is already infected and it’s too late for prevention. Once the gray mold develops, the fungus is already spreading its spores, so it’s important to remove the infected plants from the space beforehand", says Ziv. 

"For these reasons, it’s very difficult to manage bud rot outbreaks once they begin. The best way to avoid it altogether, is to prevent the conditions it needs in order to develop." 

Humidity is the #1 cause of bud rot
Ziv explains every disease needs specific conditions to develop. "In the case of bud rot, it needs free water. If you irrigate properly and grow in a greenhouse, or indoor, the only way for water to appear is through high humidity."

"When humidity is very high, as it naturally is in any space with plants, water begins to condense and appear on different surfaces. This is called the dew point, and it happens when the air reaches saturation, or 100% relative humidity."

Unfortunately, the inside of a cannabis bud has the perfect conditions for condensation to happen. "It’s naturally humid, due to transpiration, and the dense shape makes it hard for the moisture to escape. This is why bud rot is such a widespread issue in all cannabis grows, around the world. And since humidity is absolutely necessary for bud rot to develop, the best way to prevent is by limiting humidity in the space." 

Prevent mold with dehumidifiers
"It’s no surprise that using dehumidifiers to control humidity is the best way to completely prevent the conditions for bud rot", says Ziv. " A proper dehumidifier, which is designed for cultivation, can maintain ideal humidity levels at all times, providing the best defense against bud rot." 

Dehumidifiers remove moisture from the air by condensing water inside the system. They not only reduce humidity, but also provide large amounts of usable water, which is a very welcomed side effect.

"Using dehumidification is the most comprehensive and efficient way to control humidity. Other methods, such as ventilation and heating, or HVAC, have their pitfalls. As they don’t act directly to extract moisture from the air, they’re much less efficient, and require excessive heating and oversized systems just to achieve acceptable results." And, with energy prices rising, it’s important to operate with the most efficient systems to maintain profitability.

Use air circulation to prevent humid microclimates
Keeping humidity low in the greenhouse or grow room provides the first layer of protection against bud rot. But cannabis plants transpire massive amounts of water, which can overlap to create pockets of moisture, even in a low humidity environment.

These are called microclimates, and they’re especially problematic in crowded grow rooms, with thick foliage surrounding the dense cannabis buds.

Growers use various fan technologies to create air flow and disperse these microclimates. "However, directional fans, both horizontal and vertical, create a gradient, meaning conditions won’t be the same everywhere", says Ziv. 

"Humidity may be kept at bay close to the fans, but bud rot might still develop in a humid pocket of air in a far corner. Once it starts to spread, reducing humidity won’t help, so it’s important to eliminate all microclimates ahead of time."

That's why Ziv points to the concept of air circulation. "Air circulation is a unique air flow distribution concept, which disperses air in 360°, ensuring uniform conditions everywhere in the space. Combined with dehumidification, this provides the ultimate coverage and protection from bud rot and other common molds, like powdery mildew." 

Keep humidity low post-harvest & GMP & GAP certification
Reaching harvest time without bud rot requires a lot of attention. But it doesn’t end there. "Molds can still develop on cannabis after harvest, during the drying and curing phases, and even inside the final packaging. So it’s crucial to keep humidity levels low throughout the entire process, and ensure the end-product is properly dried before packaging." 

"Preventing the conditions necessary for mold development is one of the key requirements to receive GAP and GMP certifications. So it’s important to ensure low humidity throughout the entire process, from seedling to final, packaged product." 

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