Here's Why You Should Worry About Moldy Cannabis

On any given month, you’re likely to hear about a recall or a warning about moldy cannabis coming from one of the legal US states or Canadian provinces. The Canadian cannabis multinational Canopy Growth recently had to beat back rumors that moldy cannabis posted on social media reflected the quality of product at one of its Ontario grow-houses (VP of Manufacturing Mario Castillo traced it to a condemned batch ruined by an “irrigation system failure” over the holidays.). In California, a batch of packaged cannabis flower was recalled in January due to contamination of aspergillus, a black mold with spores that can cause lung infections in immunocompromised people. And debate was stirred in Connecticut when a testing laboratory asked to raise the limits on acceptable levels of colony forming units per gram for molds and yeast.

So what are the issues surrounding moldy cannabis? In this piece, we’re going to explore some of the nastiest infestations that can get into cannabis flower — stuff that a grower is constantly fighting against during cannabis growth cycles.

THE USUAL SUSPECTS

Botrytis: This foliar pathogen is not just a pest for cannabis growers — it also infects strawberries, tomatoes and many other fruits. Amongst some wine growers, it’s referred to as “noble rot,” because an infestation can concentrate the grape’s sugars in some strains. But there’s nothing noble about it for cannabis growers. Once it takes root, usually in moist, temperate and highly humid spaces, it can create hard-to-control spore surges that can infect an entire crop. It’s often noted for a brownish-grey growth that can overtake the entire bud.

Aspergillus: There’s hundreds of species that can be tied under the aspergillus umbrella (or “sprinkler,” the Latin word of which this mold gets its name). You’re most likely breathing millions of its spores right now, and, according to medical experts, usually people with healthy immune systems aren’t affected by it. However, those who are affected can come down with one of several diseases called aspergillosis, which can create life-threatening infections in the immunocompromised. Those who are susceptible to it are urged away from handling outdoor soils or packaged mulch or soil mixtures. A study of commercial cannabis plants found Aspergillus Niger on unpasteurized coco fiber growing medium.

Penicillium: Next to Aspergillus, Penicillium pops up frequently in indoor environments. Prevalent in citrus fruits, melons and used in some cheesemaking processes, it’s a major component in most food spoilages. And while one of its namesakes enjoys a sterling reputation as one of the world’s most important — if overused — antibiotics, it also can wreak havoc amongst those with weakened immune systems.

SPOTTING THE CULPRITS

Some mold/fungal infections will be obvious. Botrytis may eventually manifest as brownish-grey rot after eating the bud from inside, making the bud crumbly. Powdery mildew presents as a powdery dust that may seem resinous at first glance. Similar to moldy bread, some buds may sport hairy yellow or gray tumors or black/grey spots. The smell also gives it away too — think of musty laundry or even urine.

SHOULD I WORRY?

For the same reason you would not want to live in a house overtaken by mold, you’re best advised to avoid moldy cannabis. A 2018 study associated the presence of molds such as aspergillus and penicillium with self-reports of headaches, dizziness and other symptoms of distress in first responders shutting down illicit grow sites in Belgium. Fungus spores are virtually everywhere, and some of them are crucial to the overall health of the plant species they inhabit, particularly some penicillium species. However, they can certainly cut back on the flavor and the effect profile of any cannabis bud you might smoke or vape, and also contaminate any edible made with them.

Unfortunately, heat and even water filtration doesn’t seem to kill these fungi. Your best bet is to treat cannabis flower like any perishable good, and to purchase it as soon after harvest time as possible. We also highly recommend you read our previous article on storage, in case you’ve bought in bulk and wish to store your buds for another time.