For cannabis indoor culture, Botrytis cinerea is one of the toughest most dominant parasite fungi. Botrytis cinerea spores are found almost everywhere in outdoor air and are found as common contaminants in about half of indoor environments in the North America with average concentrations of about 45-49 CFU/m3. Chemical control and standard greenhouse keeping practice often fail to limit powdery mildew invasions and other proven disinfection technologies such as germicidal ultraviolet are being used more and more. Our experience has shown that a well-engineered combination of air filtration and air coil treatment with germicidal UV can drastically reduce the outbreaks of mildew in greenhouses. Such a system requires high levels of air changes per hour with filtration complemented by germicidal UV, and continuous UV surface decontamination of all cooling and heating coils within the facility.
The author is grateful for the contribution of Mr. Robert Renaud, Mr. Raymond Gatt, Mr. Keith Jordan, and Mr. Jean-Louis Bonneau for their valuable field experience feedback and suggestions in writing this paper.
Cervantes, G. (2006). Marijuana Horticulture: The Indoor/Outdoor Medical Grower’s Guide. Van Patten Publishing, Costa, L., Rangel, D. E. N., Morandi, M. A. B., and Bettiol, W. (2013). “Effects of UV-B radiation on the antagonistic ability of Clonostachys rosea to Botrytis cinerea on strawberry leaves.” Biological Control 65, 95-100.
Heuvelink, E. (2006). “Reducing Botrytis in greenhouse crops: periodic UV-light treatment in tomato plants.” , Wageningen University, Horticultural Production Chains, Wageningen, Netherlands. Kowalski, W. J. (2009). Ultraviolet Germicidal Irradiation Handbook: UVGI for Air and Surface Disinfection. Springer, New York.
Latorre, B. A., S. Rojas, G.A. Diaz, H. Chuaqui (2012). “Germicidal effect of UV light on epiphytic fungi isolated from blueberry.” Cien Inv Agr 39(3), 473-480.
Marquenie, D., Lammertyn, J., Geeraerd, A., Soontjens, C., VanImpe, J., Nicolai, B., and Michiels, C. (2002). “Inactivation of conidia of Botrytis cinerea and Monilinia fructigena using UV-C and heat treatment.” Int J Food Microbiol 74, 27-35.
Mercier, J., Baka, M., Reddy, B., Corcuff, R., and Arul, J. (2001). “Shortwave Ultraviolet Irradiation for Control of Decay Caused by Botrytis cinerea in Bell Pepper: Induced Resistance and Germicidal Effects.” J Amer Soc Hort Sci 126(1), 128-133.
Nigro, F., Ippolito, A., Lattanzio, V., DiVenere, D., and Salerno, M. (2000). “Effect of ultraviolet light on postharvest decay of strawberry.” J Plant Path 82(1), 29-37.
Schumacher, J., and Tudzynski, P. (2011). “Morphogenesis and Pathogenicity in Fungi.” Current Genetics 22, 225-241.
Shelton, B. G., Kirkland, K. H., Flanders, W. D., and Morris, G. K. (2002). “Profiles of Airborne Fungi in Buildings and Outdoor Environments in the United States.” Appl & Environ Microbiol 68(4), 1743-1753