Fungus affects plants when the growing humidity reaches or exceeds 50 percent.
The main culprit on cannabis is Botrytis; the same gray, powdery mold so prized by dessert winemakers is a pest for cannabis breeders. The Botrytis, or gray mold, affects all stages of the plant from seeds to mature flowers and can have significant health effects if handled or smoked. Luckily, the condition is well-known and treatable.
The first step is to reduce your humidity. This is, after all, the reason you have fungus problems in the first place. This can be achieved by more efficient control of air, either by increasing air throughput or by relocating your plants to better take advantage of the available airflow. Ensure that your air filtration system is working efficiently. If necessary, increase the volume of the filter by adding additional filtration units.
Is your lighting bright enough so that it penetrates deep into your marijuana plants, not just from overhead? It is important to ensure that adequate light falls on the plant from a horizontal direction as well, so as to more closely mimic growing in natural light. There’s one thing fungi hates, and that’s light! Using white-painted reflector boards to ensure adequate light is reaching the Marijuana Strain is the most effective method. If necessary, increase the number of lights in use.
Heat has to be adequate as well. The perfect growing conditions are a temperature of 65-70 degrees Fahrenheit and humidity of 40 percent, so it’s a balancing act. If you have too much humidity, you need to increase your extraction. If increasing airflow results in a temperature drop, you have no choice but to add more heat.
Temperatures that are too high inhibit root and leaf growth, as well as inviting pests into your farm. By keeping your root-level temperatures at around 65 degrees Fahrenheit you will inhibit mold, remain unattractive for bugs and still be warm enough for good plant development.
Sanitation is your friend. Ensure that your workers are observing good plant hygiene; make sure you are using sterilized soil, that your growing containers are clean, that you have a bleach-based foot bath outside the entrance to your grow room. Don’t grow foreign plants in your cannabis grow room.
Treatment of fungus-affected cannabis plants is relatively straightforward. The main treatment regimen is a complete spray every two weeks with a 1% Bordeaux mixture (copper sulphate, hydrated lime and water) or .5% Burgundy mixture (copper sulphate, soda ash and water) on affected plants, until the mold has gone.
Bordeaux/Burgundy mixtures can be used as a preventative fungicide as well. The fungus spores landing on Marijuana Strains treated with the copper mixture will not thrive.
Don’t stop treatment when you can’t see any more mold. You must continue to spray every three weeks right up until your plants are starting to flower.
Removing fungus-affected leaves is a must. Be ruthless! It is better to lose some foliage than to end up with a crop of fungus-infested buds.
Browse the Seedbank to find mold resistant Marijuana Strains.
Watering at the base of the plant instead of watering overhead can significantly reduce the likelihood of fungi, as well as being used for fungi reduction in affected plants. There is nothing fungi like more than dampness, so starve them of it. Ensure your growing medium is free-draining. If necessary, re-pot and introduce a specialist growing medium.