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MONTPELIER — Cannabis cultivators are always trying to stay away from troublesome contaminants.
“Last year was a really challenging year especially for fungal pathogens,” Christine Motyka, compliance agent with the Cannabis Control Board, said in a presentation given as part of the board’s Peer Networking Event series.
Her talk focused on the plant pathogen, septoria, and the human pathogen, aspergillus. She advised that “sometimes the cure is worse than the disease,” and “prevention’s the best medicine.”
“Every environment is different,” she said. “There’s no single solution. It’s a difficult situation and you just want to be very cognizant that your environment has its own perfect solution, and not everything that works for someone else is going to work for you.”
Motyka urged constant experimentation in cultivation. She called good sanitation “the cheapest and most effective pest management method.”
Weekly scouting can help manage pests and diseases, Motyka advised. She said that “they favor some of the same environments that our plants need.”
“Fungal organisms are microscopic so you’re not going to see early outbreaks,” she said.
She described how septoria leaf spot starts on the lowest part of the plant: small yellow spots will develop with brown centers then spread upward and eventually kill the leaf.
Septoria cannabis uses cannabis as a host. Motyka said there are likely other species of septoria that also will use cannabis as host, however, it’s unlikely that every leaf spot on every tree and plant surrounding an outdoor cultivation operation is a disease that can also use cannabis as a host.
“It’s scary looking at the amount of other diseases that might be on plants around your cultivation,” she said. “It is again unlikely that most of those will also infect your crop but there definitely could be some overlap.”
Motyka said rain and high humidity, as seen in Vermont last year, allow fungal organisms to reproduce and climb plants. She stressed the importance of spacing plants and maintaining good airflow.
To limit contact with soil, she suggested removing the lowest branches that might touch the ground.
“Mulching to cover the soil surface can be helpful,” she said.
She recommended using biological fungicides from a list of what’s allowed in cannabis cultivation in Vermont. If space allows, rotating cultivation areas is advised.
Pruning should be done in dry weather and leaves removed from the plant should be taken out of the cultivation area, Motyka said.
“You want to be as careful as you can with tools, handwashing,” she said. “Make sure everything is as sterile as you can as you move through your cultivation area.”
Aspergillus likely involves an “accidental landing on your plant and you’re not going to see more covering your plant,” Motyka said. She described it as a fungal organism, with more than 185 species, found in soil, vegetation, decomposing matter and water.
“The reason that we test for it is it can produce mycotoxins and cause aspergillosis, which is a serious infection in humans,” she said. “When archaeologists first started breaking into the Egyptian tombs, it was thought that they were cursed because many of these archaeologists died soon after opening these tombs, and is now known that aspergillus was living on those mummies and caused disease in those archaeologists so it’s serious stuff.”
Motyka said aspergillus can grow in a wide range of pH and temperature environments.
“Everyone’s vulnerable to failing these tests because it’s just so common in the environment,” she said. “Your sampling methods could also be a source of contamination.”
Motyka said containers and bags should be clean, sanitized and handled with gloves. Disinfecting surfaces also can help keep aspergillus away.
