Handling Botrytis (Grey Mold) in Cannabis

What is Botrytis? Also known as “Botrytis Blight” or “Grey Mold”, Botrytis is a fungal disease. This fungus forms a grayish powdery mold on a variety of organic matters and leads to the rapid and complete chlorosis or yellowing and then death of plant tissues.

Like most molds, Botrytis is best controlled by preventative care rather than reactive care. Once it establishes a good foothold in your crop, its hard to completely get rid of.

Here are some of the precautions you can take to help control it.

1. Proper Spacing Between Plants: In areas where you can’t control the humidity, having plants too close together can promote the growth of all mold, including Botrytis.
   
2. Prune Any Dead or Effected Areas ASAP:  Botrytis attacks dying parts of a plant, so removing these parts quickly is the best way to prevent your plants from being an easier target. Pruning any leaves or parts of the plant that have the early stages of Botrytis will keep it from spreading. When trimming already effected areas, make sure to make a clean cut a few inches below the effected area, or it may come back. Also remember to disinfect the trimming scissors that were used.
   
3. Look For Injuries On Your Plants: Gray mold tends to go after cuts or wounds on plants (from trimming tools, bugs, high winds or over handling) so minimizing and healing these on your plants will help control the fungus.
   
4. Thoroughly Clean Your Environment After Harvest: If possible, cleaning your grow environment with a bleach solution AFTER you’ve completely harvested will be important to prevent it from returning next year. Spores from this years mold can actually remain in the area and the soil and effect next years plants.
   
5. Increase Nutrients: Like I mentioned before, Botrytis mainly attacks dead or dying parts of the plant. If you have a lot of this on your cannabis, it may be caused by nutrient deficiency. With this in mind, an increase in nutrients should lead to a decrease in dead parts of the plants which will decrease the amount of places for the mold to develop.
   
   Depending on what industry you’re intending to sell your cannabis for, I would not advise adding any pesticides on the plant to destroy the mold unless all else has failed. Adding a pesticide to an entire crop to prevent one problem may lead to 10 more while trying to sell the product. In the early years of legalization, pesticide use is frowned upon but accepted as necessary. However, because of the green nature of the business, many wholesale buyers tend to shy away from product that isn’t organically grown. It all depends on what the hemp is intended for, but it is a buying factor to keep in mind if you’re selling your product wholesale.