What is Aspergillus?
Aspergillus is a type of filamentous fungus commonly found in soil, decaying vegetation, seeds, and grains. It does not require a living host, but can grow in dead and decaying material and harvested crops.
There are over 200 species of aspergillus, and they are very common. This is because aspergillus grows in many forms of organic matter, in a wide range of temperatures (42⁰-131⁰F) and in low relative humidity levels compared to other fungi (80 - 98%). Because aspergillus grows so easily, many people breathe airborne aspergillus spores regularly.
While most exposure is harmless, some strains of aspergillus are considered dangerous and can cause infections, fatal diseases, and allergic responses.
Is Aspergillus a Concern?
Most people can easily avoid aspergillus in their homes by maintaining a clean kitchen and bathroom, and keeping plumbing in good repair. But avoiding aspergillus can be more a difficult task in agricultural settings.
Grape, hops, and cannabis growers often have large amounts of plant material in one place, and aspergillus growth is always a risk. Harvest, storage, and curing are particularly susceptible stages for the crops, but infection can begin while the plant is alive. The fungus lies mostly dormant until the crops are harvested then rot develops.
Aspergillus in the Cannabis Industry
Some of the most harmful effects of aspergillus are caused when the spores are inhaled. This is a particular concern in the cannabis industry. The danger and prevalence of aspergillus has led cannabis industry regulators to put in place stringent requirements to identify the presence of aspergillus.
The strains of aspergillus that pose the biggest threat to human health are Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger, and Aspergillus terreus. Most state cannabis programs will not allow product with any concentration of these aspergillus strains to be sold.
Many cannabis growers struggle with aspergillus, and some have had product recalls after their products hit the market. High profile examples in Nevada and Florida have raised health concerns that shaped the industry and its standards.
“I have helped a number of operators deal with their aspergillus problems. Seeing product test positive for aspergillus can be crushing for growers. It puts their income at risk, and even worse, it can put their customers at risk if not treated properly – and a lot of them don’t know where to start,” said Darrin Potter, a nationally-recognized horticulturist and consultant.
How to Prevent and Treat Aspergillus?
To keep people and agricultural products safe from aspergillus, it is important for growers to keep a comprehensive integrated pest management regiment, including:
- Diligent disinfecting of work surfaces;
- Proper PPE use;
- Environmental control management; and
- Avoiding moisture and condensation on susceptible surfaces.