Brotytis or Gray Mold
Botrytis, or Gray Mold, is probably the most common disease affecting cannabis crops worldwide. It is very prevalent when humidity is high during the flowering stage of the cannabis plant. When humidity is high, the fungus develops a gray mold on the affected tissues, a characteristic feature of this disease. The mold is a layer of mycelium and fruiting bodies with numerous conidia that cause secondary infections, while the mycelium invades the rest of the affected tissue. When humidity is low, the mycelium that develops is tan and appears as leaf spots.
In severe cases, the fungus can cover the tips of the cannabis plant with its mycelium. These plants must then be discarded due to their high toxicity.
This fungus attacks cannabis at all stages of its growth. In seedbeds, it can attack seedlings from a very early age and even during germination.
Brotytis or Gray Mold Video
Gray mold infections spread to rooted cuttings; high relative humidity favors the development of this pathogen on leaves and wounded stems. The fungus takes advantage of the wounds caused by pruning shears to penetrate and begin its life cycle.
The symptoms following a severe Botrytis infection include necrosis of the weakest and most damaged tissues. On leaves, a uniform chlorosis may appear around the necrotic area, while on herbaceous tissues, a watery appearance may develop. When conditions are favorable for fungal growth, such as high humidity, the pathogen develops conidiophores laden with asexual spores. A splash of water or simply moving infected plants is enough to release the conidia and spread the fungus to other healthy plants.
Control method
A very effective control method is prevention through climate control, increasing overall ventilation to reduce nighttime humidity in the cannabis grow area. Proper mineral nutrition is also a good control method.
Another control method is to use fresh substrates for seedbeds. If the substrate is reused, it must be disinfected beforehand with steam or a specific product. Applying a systemic fungicide or silica rock powder has proven quite effective in preventing these fungi by inhibiting spore germination. A popular and effective technique is the application of symbiotic microorganisms that act as antagonists of the pathogen.
Removing dry plant debris from the facilities will be a task to be carried out, as this pathogen can take refuge in this debris.
To control Botrytis attacks during rooting, extreme disinfection of all materials used, and in particular of mini-greenhouses or propagators, must be carried out.
Excess water in the environment often favors gray mold attacks, therefore puddles and high humidity conditions should be avoided.
When it comes to feeding cannabis plants, the nutrient solution should be richer in potassium than in nitrogen. Plants with excess nitrogen will always be less resistant to attacks from Botrytis, other parasitic fungi, and pests.