Agriculture is in our blood, the practice of farming is what most influenced the organization of humans into the various social orders of early civilization. Archaeologists have recognized signs of Cannabis horticulture dating back to ancient times. It should come as no surprise that almost anyone with access to a small plot of land, or even a sunny patio with a few half wine barrels; feels the primeval urge to scatter a few seeds. Be they ornamental flowers for beauty and fragrance, or yummy common veggies like lettuce and tomatoes; there is a deep satisfaction which comes from growing your own nutritious and clean food. Likewise, as the taboo of prohibition lifts across our country and indeed the world, more and more folks are trying their hand at personal Cannabis horticulture.
There’s no shortage of anecdotal information on the Internet about growing Cannabis. Dispensary bookshelves and magazine racks are lined with how-to guides, some of it quite accurate and scientific. But because of its Schedule 1 status, little or no University research exists on best practices for Medical Marijuana crop farmers or home gardeners. Fortuitously, the pests and diseases which plague Cannabis closely parallel one of the world’s most studied and well understood crops – Tomatoes. I believe that personal Cannabis grows can be demystified and mastered by using the Tomato as a proxy or model.
Botrytis, or Gray Mold, prospers in overly humid environments, its microscopic spores enter the plant through wounds and abrasions which can be caused by pruning, or wind driven rubbing against supports and ties. On Tomatoes the damage is easily recognized as stems are girdled and fruits ruined. ( http://www.ipm.ucdavis.edu/PMG/r783103211.html ) On Cannabis the damage often goes unnoticed until the precious fully developed female flower bud complexes or “Colas” become infected and spoiled. ( http://edrosenthal.com/2012/08/ask-ed-marijuana-grow-tip-44-the-botrytis-solution.html )
To check the spread of Botrytis as organically as possible start with mechanical methods, prune away minor infections but don’t be shy about yanking out or sacrificing an entire diseased plant to spare others the infestation. Progress to natural products containing oils with proven fungicidal effects such as cinnamon and clove as needed. As a last resort consider natural biological control; Serenade is a product containing specialized bacteria which colonize the plant and suppress the spread of Botrytis.
Prevention is key; eliminate opportunities for leaf and stem contact with moist soil, control humidity, remove and dispose of dead, damaged or diseased plant material. Resist the temptation to shop the local big box garden center for potent convenient exotic chemicals promising instant cures. Why would you taint clean medicine with poison?
Disclaimer: Any advice and opinions offered about the cultivation of cannabis by Bruce N. Goren are his own and do not represent the University of California or the Master Gardener Program.