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Microbial Contaminant Remediation, Molds and Fungi in Cannabis

As the cannabis industry emerges, many questions surrounding the safety and efficacy of cannabis remain unanswered. In contrast with almost all other industries in the United States, where products are grown for human consumption and/or medical use, the cannabis industry has virtually no guidelines, limitations, or quality assurance mechanisms in place to protect its employees and consumers, aside from those provided by third parties such as Steep Hill. As a result, the quality of cannabis can vary widely from season to season, farm to farm, between growers, collective dispensaries, and even day to day within the same collective. An industry wide lack of standardized practices and remediation strategies virtually ensures that this will continue. This writeup aims to help providers begin a path towards effective quality assurance over the medicinal products they provide to patients, and become leaders in the industry in the process.

Molds are biological organisms in the Fungi kingdom. There are many thousands of species of mold in the world. Molds are everywhere. They are in the air we breathe, the food we eat, and the water we drink. Many molds are innocuous, yet many others are potential human pathogens. All molds require moisture to live and reproduce, but mold spores can survive exceptionally extreme conditions devoid of water or warmth.

Certain molds seem to continually reappear in the medical cannabis supply. Many of them are fairly ubiquitous and most likely would appear on many similar large leafy green plants. Plants themselves make exceptionally good ecosystems, and generally support a large biological array of species. They are excellent sources of water and sugar, which many animals, bacteria, and molds require for survival. Cannabis is no different, and just about any plant, whether it is grown indoors or outdoors is usually teeming with life.

Under average conditions, you are more likely to find mold spores on a plant that is outdoors. Most molds live outside where there is ample access to water and food. But molds that are outdoors are also more likely to be kept under control by natural checks and balances. Indoors, if molds are able to gain a foothold natural checks are generally lacking, and a small problem can quickly grow to be an epidemic. In grow rooms, the problem is usually exacerbated by high levels of heat and moisture. Once mold is able to gain a foothold inside, it can be extremely difficult to regain control of the situation.


The following is a list of typical molds found on mold in California in order of increasing rarity: Powdery Mildew, Penicillium, Yeast, Aspergillus, Cladosporium, Fusarium, Botrytis, Aureobasidium, Acremonium and more…..

The main key to preventing mold is controlling moisture. For outdoor growers, this can be very difficult. In the late fall, the likelihood of rain increases with each passing day. Once it rains, the soil often becomes saturated and water remains condensed on the underside of leaves and in the tight space between flowering tips. One of the worst things that can happen to an outdoor grower is for a period of rain to be followed by a warm windless sunny day. If this happens, the area underneath the canopy and nearest to the soil can become like a sauna, and a mold explosion can ensue. There are techniques that can be used to limit the risks associated with a rain event. Completely removing all vegetative material on the underside of the plant within the first 2-3 feet nearest the soil significantly increases airflow under the plants. Air flow will evaporate moisture faster reducing the period of time most amenable to mold growth.

Indoor growers will find that they are better able to control the moisture of their grows. They should expect to invest a decent amount of money into a quality dehumidification system. Relative humidity should be kept at or below 55%. While less important indoors, reducing vegetative material in the few inches nearest to the growing medium can be helpful.

Most molds prefer environments that are on the slightly acidic side. It can therefore be helpful to perpetuate conditions are alkaline. Alkaline water itself can go a long way toward reducing the risk of a powdery mildew mold (PMM) infection. Neem oil can be helpful in eliminating PMM, but is also useful as a preventative measure. Some advanced growers, especially in greenhouses where the risk of mold infection is high, have begun using foggers and nebulizers with anti-fungal compounds. In greenhouses, where the risk is highest these devices maybe used as much as 16 hours a day. This can almost guarantee the elimination of the risk of mold infection. Animals should be kept out of indoor grows and cure spaces. Dogs and cats will shed dander, and can bring any number of unwanted mold and bacteria into your workspaces. In all grows, plants that are weak or sick should be destroyed and removed from the garden. Weak and sickly plants generally have weakened defenses and can be a target for any number of diseases and pathogens.

Microbiological Contamination Is More Common Than Most Cultivators Realize.

PACKAGING AND HANDLING – Medical cannabis should be handled on clean surfaces. Vending and weighing surfaces in dispensaries should be made of glass, stainless steel, or some other surface that is non- porous, and can be easily cleaned and sterilized when necessary. Scale surfaces should be cleaned between batches. Use methanol, or some other non-toxic cleaning agent to wipe surfaces. Ideally sterile wipes should be used to assure the highest levels of cleanliness.

Every person who handles medical cannabis after it is cut down should wear gloves. Use clean fresh packaging. Standards such as oven bags are acceptable. Do not re-use these bags. Sealable vacuum bags also work well. Sterile bags are available and should become the standard over time.

Medical grade cannabis should never be placed on the ground. Do not package it in unclean areas. It should not be handled in rooms with carpet. The shaggier the carpet, the higher risk it will retain contaminates and other risk elements. Carpeted handling areas are undesirable in general. Collectives should only handle medicine on counters that are above waste level.