Preventing Aspergillus Contamination in Cannabis Crops

As cannabis makes the uphill climb away from taboo and towards social acceptance (and someday, legalization), we’re seeing increasing conversations surrounding customer and patient safety. One of the current, significant challenges faced by cannabis cultivators is preventing the growth of Aspergillus, a common fungal contaminant. Presently, the spotlight is on the state of Oregon, where strict regulations were put into place on March 1st, 2023.

Although the Oregon Health Authority’s (OHA) zero-tolerance regulations are to ensure the safety of cannabis consumers, cultivators and cannabis industry leaders pushed back. With the support of commercial Oregon cannabis growers, the Cannabis Industry Alliance of Oregon (CIAO) argued that the regulations are business-prohibitive. On August 25th, 2023, the Oregon Court of Appeals placed the highly restrictive Aspergillus testing policy on hold until the court can arrive at a fiduciarily responsible decision.

Still, safety is undeniably important when it comes to manufacturing cannabis products. And we firmly believe that prevention is the best solution to avoid this fungal contaminant and avoid costly remediation. Understanding the types and characteristics of Aspergillus mold can help cultivators identify, prevent, and mitigate potential health implications to consumers.

testing cannabis plants
Testing new plants before they are introduced into your growing area can help prevent unwanted molds, viruses, and pests from infecting your plants. It’s also important to regularly test your established crops to ensure they have not been infected by a contaminant that may have found its way into your facility.

Next, we’re going to delve into the science behind Aspergillus, exploring its classification, characteristics, and risk factors. And most importantly, how cultivators can implement preventative strategies.

Overview of Aspergillus

First things first. Aspergillus is a type of mold, and molds are a type of fungus. Although all mold is categorized as fungus, not all fungi are classified as mold. We could dive in deeper, but suffice to say, Aspergillus is a mold within the fungi kingdom. The easiest way to remember the difference is that mold reproduces and spreads using spores rather than branching out like fungi using filaments called hyphae.

There are dangerous variations of Aspergillus, and they’re everywhere. This is quite the challenge for cultivators operating in an industry where allowing your buds to break down (curing) is the perfect bait for dead-matter-loving mold.

For those of a curious nature: mammals ingest food, plants biosynthesize their own (through photosynthesis), while fungi and mold absorb their food. This is one of the differentiating characteristics between the three kingdoms. As we’re not mycologists, we’ll move on with the knowledge that we’re dealing with a very resilient type of mold/fungus that loves cannabis as much as the rest of us.

Characteristics of Aspergillus Mold

It’s common knowledge that mold creates headaches for cannabis cultivators (figuratively). Growers are always combating mold and trying to mitigate spore reproduction. The genus Aspergillus is divided into several types (known as subgenera and sections) based on various criteria such as morphology, reproduction, adaptability, and mycotoxin production.

  • Morphology: Aspergillus colonies typically appear cottony or woolly in texture and often display various colors, such as white, green, yellow, or black. The fungus forms long branching filaments called hyphae, which extend and intertwine to form a dense network known as mycelium.
  • Reproduction: This type of eukaryotic life reproduces through the production and dispersal of spores. These spores are microscopic, lightweight structures that can be easily carried by air currents. The ability to produce vast quantities of spores enables Aspergillus to colonize new environments rapidly, including cannabis grow rooms.
  • Environmental Adaptability: Aspergillus is highly adaptable and can grow over a wide range of temperatures, pH levels, and moisture conditions. This resilience allows the mold to thrive in diverse environments, from damp corners of buildings to decaying vegetation.
  • Mycotoxin Production: Certain species of Aspergillus have the ability to produce mycotoxins, harmful compounds that can have serious health implications for humans and animals. For example, the species Aspergillus flavus can produce aflatoxins, which are potent carcinogens and pose a significant food safety concern.

Types of Aspergillus Mold

There are several types of Aspergillus molds, each with its own unique characteristics and health implications. The most well-known and medically important species include fumigatus, flavus, niger, and terreus. These types are commonly associated with various contagions and are the focus of much scientific research. Here is a breakdown of these four types:

Aspergillus Fumigatus

This species is the most prevalent and virulent type of Aspergillus mold. It is commonly found in compost piles, decaying vegetation, and soil — all places prevalent in the cannabis industry. Fumigatus can cause severe respiratory infections (such as aspergillosis) in individuals with compromised immune systems. In severe cases, an Aspergillosis infection can cause masses of fungus in the lungs (aspergillomas) and then spread throughout the body. This, of course, requires acute medical care to resolve.

Aspergillosis Infection
Aspergillosis is a respiratory infection that is caused by Aspergillus mold. When aspergillosis infects the lungs, it can result in a fever, chest pain, and coughing up blood in severe cases. These extreme cases require immediate medical attention. The risk to the end-user can be mitigated by ensuring your flower is not infected with Aspergillus by means of professional testing.

Fumigatus can tolerate higher temperatures, making it one of the larger threats to cannabis manufacturers since lighting up a joint doesn’t create enough thermal energy to kill the organism should it be present in the flower. Due to its thermal resistance, it is frequently found in compost heaps and decayed organic matter. This means that it can still survive, spore, and spread from burnt, infected flower.

Aspergillus Flavus

Another species of Aspergillus, flavus, is commonly found in agricultural settings, particularly in grains and nuts. It produces aflatoxins, which are potent carcinogens and can contaminate food products. This poses serious health risks when ingested in large amounts. This species of Aspergillus is also one of the types that can commonly be found infecting cannabis plants.

Aspergillus Niger

Aspergillus niger is a black-colored mold commonly found in decaying food, soil, and indoor environments. While it is generally considered to be a non-pathogenic species, it can still cause allergic reactions and respiratory issues in sensitive individuals. It is commonly known as black Aspergillus mold.

Niger is often found in tropical and subtropical regions and is known for its production of mycotoxins, such as aflatoxin. If you are cultivating cannabis in a hot and often humid region, this species of mold could be a threat to your crop.

Aspergillus Terreus

Much like other species of Aspergillus mold, terreus is typically found in soil and decaying plant material. Again, a real bummer for cannabis cultivators. And if the flower is stored in unsuitable relative humidity (too damp), it could be at risk if terreus is brought into the burping room.

The species is known to produce a variety of secondary metabolites, some of which have antibiotic properties. Although not as dangerous as several of the species above, it can still cause invasive infections in individuals with weakened immune systems.

The Impact of Aspergillus on Cannabis Cultivation

When Aspergillus spores land on cannabis plants, they can colonize and thrive in the warm and humid conditions commonly found in cultivation facilities. As the mold grows, it can release mycotoxins, which can contaminate the plant material and potentially spread to other products in the facility. Aspergillus contamination not only poses health risks to consumers but can also result in product recalls, damaged branding, and legal consequences for cultivators.

While most strains of Aspergillus are harmless, certain species (such as the ones we discussed above) can be harmful if consumed or inhaled. One of the first steps in mitigating Aspergillus is to understand the conditions that allow it to thrive.

Factors Contributing to Aspergillus Growth

Unfortunately, the propagation of Aspergillus mold is influenced by several environmental factors commonly found in commercial grow rooms. These conditions include moisture, temperature, access to organic matter, and air circulation (or a lack thereof.) Many of the same conditions that increase your yield encourage the growth of mold and fungus. And if you’re a cannapreneur, we know we’re preaching to the choir.

Conditions that increase your chance of Aspergillus:

  • Moisture: Moisture is essential for Aspergillus mold growth. High humidity levels, water leaks, or condensation can create a favorable environment for mold spores to germinate and proliferate. Airflow can help mitigate this risk.
  • Temperature: Aspergillus molds thrive in temperatures ranging from 20 to 30 degrees Celsius (68 to 86 degrees Fahrenheit). This temperature range is conducive to their growth and can promote rapid colonization. It’s best to eliminate mold and fungus before creating the perfect conditions for them to thrive.
  • Organic matter: Aspergillus molds require a nutrient source to sustain their growth. They can utilize a wide variety of organic matter, including dead plant material, food, and even dust particles.
  • Air circulation: Poor air circulation can contribute to the growth of Aspergillus molds. Stagnant air provides an environment where spores can accumulate and settle on surfaces.

Cultivators have to dance the delicate ballet of maintaining optimum growing conditions while battling mold and fungus who love to join in on the fun. If you have mold under control, then you’re on the right track. However, if mold keeps sneaking into your growing environment, we’ll provide some tips further down to help fight back in the battle against this hardy organism.

Prevention and Control of Aspergillus

Under ideal conditions, strict operating procedures, and adequate training, a grower can try to prevent an Aspergillus outbreak in their crop. However, realistically, it’s likely you’ll need to control and mitigate Aspergillus mold at some point. Tightening up sanitation protocols, installing efficacious air filtration, and conducting regular training and testing, can all help keep Aspergillus (and other types of molds and fungi) at bay.

Maintain a Clean, Sanitary Facility

One of the most critical steps in preventing Aspergillus contamination is maintaining a clean and hygienic cultivation facility. Cultivators should implement robust sanitation measures to ensure that the environment remains free from mold spores and other contaminants. Some best practices to consider include:

  1. Adequate ventilation: Proper ventilation helps to reduce moisture levels indoors, minimizing conditions favorable for Aspergillus growth. Ensure that air vents are clean and unobstructed.
  2. Maintaining a dry environment: Moisture is a key factor in mold growth. Fix any leaks or water damage promptly, and use dehumidifiers in areas prone to dampness, such as basements and bathrooms.
  3. Consistent cleaning and sanitizing: Regularly clean and disinfect surfaces, particularly in areas susceptible to mold growth. Pay attention to areas with high moisture, such as kitchen and bathroom surfaces.
  4. Periodically inspect for signs of mold: Regularly inspect buildings for any signs of mold growth, especially in areas with poor ventilation or a history of water damage. Promptly address any issues to prevent mold from spreading.
  5. Use personal protective equipment (PPE): When sanitizing an area containing an Aspergillus outbreak and transporting infected plants, consider wearing appropriate PPE, including masks and gloves. This both protects your employees from potential infection and helps prevent the spread of the fungus/mold.
  6. Clean, clean, clean: It can’t be over-emphasized how important it is to keep your facility clean. Establish a schedule for all areas of the facility, including grow rooms, manufacturing rooms, equipment, and storage areas. Use appropriate cleaning agents and techniques to effectively remove mold spores.
  7. Waste management: Implement proper waste disposal procedures to prevent the accumulation of organic matter that can serve as a breeding ground for mold. Dispose of plant material, trimmings, and other waste in sealed containers to minimize the risk of mold growth.
  8. Personal hygiene: Educate and enforce proper personal hygiene practices among cultivation staff. This includes wearing clean protective clothing, washing hands regularly, and refraining from smoking or eating in cultivation and processing areas.
  9. Establish quarantine protocols: There are two primary reasons to quarantine your cannabis plants. First, when you acquire new plants, always test for mold and viruses before introducing them to your crop. Second, if an Aspergillus mold infection is detected on a plant, immediately remove the plant from the primary crop until it has been adequately mitigated. This may entail costly remediation.
Wearing PPE during mold mitigation.
If you find an area of your cannabis operation where Aspergillus (or other types of mold) have run rampant, it’s recommended to wear sufficient personal protective equipment (PPE) to protect you or your staff from contracting aspergillosis. Wearing PPE also helps prevent the spread of mold and fungus by preventing it from hitching a ride on your clothes or shoes to other parts of your facility.

This isn’t an inclusive list, but it’s a start. By diligently keeping your entire cannabis operation space clean, cultivators and processors can significantly reduce the risk of Aspergillus contamination.

Developing Effective Air Filtration Systems

Airborne transmission is one of the primary ways in which Aspergillus spores can enter a cultivation facility. Installing specialized, commercial air filtration systems is crucial in preventing mold contamination. High-efficiency particulate air (HEPA) filters are a great first line of defense in capturing spores that would otherwise circulate throughout your facility.

Airflow management can help cannabis facilities optimize the airflow patterns within grow rooms and processing labs to minimize stagnant areas where mold can accumulate. Utilizing ventilation fans to maintain consistent air circulation throughout the entire space also helps reduce damp, stagnant pockets of air where Aspergillus could take hold.

Cleaning the air is just as important as cleaning the surfaces of your grow room. By scrubbing mold spores in your ventilation system before they can land on and infect your plants, you can significantly reduce the risk of Aspergillus contamination.

Training Staff on Preventing Mold Contamination

Ensuring that your cultivation staff is trained on mold and fungus prevention is essential for maintaining a safe and compliant cultivation facility. Some key areas to focus on during training include:

  • Identification and reporting of mold: Educate staff members on how to identify signs of mold growth and the importance of reporting it immediately. Prompt action can prevent the spread of mold and minimize the risk of contamination. It also could mean the difference between losing a couple plants versus needing to remediate an entire harvest.
  • Sanitation practices: Train staff on proper sanitation practices, including cleaning protocols, personal hygiene, waste management, and quarantine procedures. Ensure that they understand and adhere to these practices consistently. After trimming a batch of cannabis, simply washing their hands helps prevent the spreading of any contagions to other plants. As an added bonus, it also helps prevent cross-strain contamination.
  • Air filtration system maintenance: Provide training on the proper maintenance of air filtration systems. This includes replacing air filters and inspecting ventilation systems for signs of mold. If you employ a third party to maintain, inspect, and clean your air system, be sure to have a schedule accessible, and someone responsible for ensuring the schedule is held to.
  • Compliance with regulations: Familiarize staff members with your state’s regulations regarding Aspergillus prevention. Ensure that they understand the importance of compliance and the potential consequences of non-compliance.

By providing comprehensive training, cultivators can empower their staff to effectively contribute to Aspergillus prevention efforts and maintain compliance with state regulations like those implemented in Oregon.

A Clean Fight Against Aspergillus

The good news is many commercial cultivation facilities are already taking preventative measures against mold and fungus. Many of these precautions also help prevent Aspergillus contamination. By implementing robust sanitation measures, effective air filtration systems, and ideal growing conditions, cultivators can minimize the risk of Aspergillus as well as other contaminants.

By maintaining regular training sessions, conducting regular testing, and staying compliant with state regulations, cultivators can ensure their crops are grown in a safe environment. Although regular Aspergillus testing adds an additional expense, the long-term savings in preventing recalls or worse may be worth the effort.

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