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Nobody likes getting sick.
And when it comes to cannabis, nobody likes getting sick plants.
Sick plants mean lower yields, lower quality, and high economic and environmental costs from trying to get a bad situation under control.
Closed growing facilities provide conditions that are very favorable to disease outbreaks. Nice, warm, humid conditions make cultivation facilities a tropical vacation spot for diseases like botrytis and powdery mildew. Throw in monoculture, dense plant spacing, and rapid growth, and you’ve got yourself an all-you-can-eat buffet for some hungry vacationers.
How is a disease born?
The recipe for disease is pretty simple, like a triangle with three sides. It only takes three ingredients:
- A host: A plant that is susceptible to infection.
- A pathogen: A disease-causing organism that is capable of infecting the host. For example, a fungus or bacteria.
- The right environment: The conditions that are right for an infection to happen.
If these three things exist at the same time for long enough, disease will develop.
Editor’s Note: The technical term for the formation of disease is pathogenesis.
What can be done?
Like a fire triangle, if you remove any of the three components for disease, you can prevent the disease. There are tools that can target each of the three requirements, and you only need to remove one to prevent the formation of disease.
One way to prevent disease is by making the host resistant or immune to the pathogen. Resistant host plants are bred to have to be genetically incompatible with the pathogen, making them immune to specific pathogens. The downside, however, is that these plants only have selective immunity to specific pathogens, and only if those pathogens don’t coevolve to develop resistance.
Pesticides can be used to target specific pathogens (such as fungi or bacteria) directly. These can be effective at removing pathogens, but there is also a high likelihood that resistance will develop in the pathogen, not to mention the toxicity and costs involved with pesticide use. If you plan on using pesticides, make sure to comply with all federal and state laws about their usage.
That brings us to changing the environment. Every disease requires a unique set of environmental conditions to take root, such as optimum temperatures, radiation levels, and humidity levels, to name a few. As greenhouse and indoor growers, we have a lot of tools at our disposal make an impact here.
Climate Control as Disease Control
Indoor, closed growing facilities give us precise control over growing conditions, inputs, and outputs. Lighting, temperature, humidity levels, irrigation scheduling, and air circulation are several factors you usually already have the means to control. So why not take advantage of the systems you already have? You can manipulate the indoor environment to produce conditions that are unfavorable to the disease, but comfortable for your plants.
Let’s take botrytis (otherwise known as bud rot or gray mold) as an example. Botrytis flourishes under conditions of high relative humidity. High humidity can lead to condensation on plants, especially in buds, where the high density of the flower creates pockets which trap moisture. The fungus uses this moisture to take root (sometimes literally) in the plant.
At DryGair, we solve this with dehumidification. With a proper dehumidification system, you can lower the relative humidity uniformly throughout the growing facility, keeping the buds and plant surfaces dry. Without moisture on the plants, botrytis spores cannot develop and thus the disease is effectively prevented.
Of course, when making adjustments to the growing conditions against disease, it is important to make sure that you are still supplying conditions that do not harm to the plant’s normal growth processes. If you turn the temperature down too low, for example, plant growth will slow or stall. Or, if you lower the humidity too much, the plant may become severely water-stressed.
Knowledge is power
In order to utilize environmental control as a preventative tool, you must know your potential threats well. When you study up on cannabis diseases, you can better understand when certain pathogens are likely to appear and when to expect problems, which environmental conditions are favorable to disease formation, and what tools you have at hand to gain control over the situation.
Rather than reacting to the problem, use the power you have at hand to prevent disease before it arrives. A well-informed grower has an effective tool kit at the ready, nipping the problem in the bud (so to speak), to get healthy, happy crops.
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About the Authors
DryGair’s writers include a team of experienced engineers, agronomists, and economists. They specialize in climate control in closed growing facilities and practical solutions for effective climate management.