Moldy Weed Is Dangerous But You Can Learn How To Detect It

Francis Cassidy December 3, 2019 2 comments

Mold is a non-scientific term that covers many types of unwanted fungi that may be found on cannabis.

The ingestion of moldy cannabis can result in allergic reactions and fungal infections that lead to chronic disease. Here’s how to ensure your medicine remains free from mold and as pure as nature intended.

The Hidden Dangers of Moldy Weed

Mold exposure can affect everyone differently. While some remain unaffected by exposure, many others aren’t so lucky. Patients who smoke or vape moldy weed may experience respiratory inflammation and infection along with accompanying chest pain, difficulty breathing, and coughing. In more severe cases, patients experience nausea, vomiting, and gastrointestinal issues.

While the aforementioned effects are unpleasant for anyone, they are especially dangerous for older medicinal cannabis patients who have already weakened immune systems.

Mold is everywhere however, not just in cannabis. It’s in the air and on surfaces and generally thrives when accompanied by moisture. The CDC (Centers for Disease and Control Prevention) takes the issue of mold seriously and has provided a solid breakdown of the effects of mold in different environments.

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Cannabis Mold Testing: TYMC and PCR

When it comes to testing cannabis for mold, the requirements differ depending on the jurisdiction. While some states specify an overall threshold for the presence of yeasts and molds, others scan for particular species of molds and yeasts during testing.

The lab testing of cannabis for mold consists of using microbiological methods that examine the cannabis at the cellular level to detect the presence of microbial impurities.

In jurisdictions where there’s a requirement for a total count of yeasts and molds, one commonly used testing method is the Total Yeast and Mold Count (TYMC).

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Testing methods intended to detect the specific species of mold strains typically analyze the presence of unique DNA sequences such as Polymerase Chain Reaction (PCR).

Why Test for Moldy Weed

Both TYMC and PCR have advantages and disadvantages. The cost, testing times, selectivity, and the sensitivity of each method varies widely.

While PCR is very sensitive and selective, the cost of the equipment required for such testing is greatly increased. TYMC, on the other hand, is easily performed and requires minimal training. This leads to a lowering of the costs involved, but one drawback is that TYMC is not species-specific.

Cultivators in states, such as Colorado and Nevada, use TYMC testing as state law requires them to test for a total mold and yeast count. Cultivators in California, by contrast, must instead test for specific species of mold that include Aspergillus mold. This means that in states where tests are chemovar or strain-specific, the more expensive PCR testing method is  employed.

moldy weed

How to Identify Moldy Weed

Supposing you’ve just harvested and cured your cannabis, how can you detect the presence of mold at home without using expensive equipment?

The precision offered by TYMC and PCR techniques is hard to replicate with the human senses. However, there are ways in which you can check for obvious signs of mold contamination.

Firstly, when growing cannabis you ideally won’t wait until harvest. The earlier you can identify mold contamination, then the less chance there is of it spreading and ruining an entire crop.

Eye-Ball Your Buds

By visually inspecting your buds, look out for anything that looks similar to cobwebs within the buds. It will almost certainly be mold.

Likewise, dark spots on otherwise green buds, or a yellow or gray fuzz is also a warning sign. Powdery mildew is another form of mold which is often similar to kief in appearance. If you notice a very fine sawdust-like powder on your buds, then this is likely mildew.

Take a Sniff

Thanks to the abundance of terpenes, good quality cannabis can have a wide-ranging array of aromas, but the smell of sweat or urine is a sure sign of mold.

While such smells are a sure giveaway, don’t rely solely on them. Recently formed mold won’t have a scent, but it’s just as dangerous and will require another detection method.

moldy weed tested under home microscope

Get up Close and Personal With a Microscope

Digital microscopes come surprisingly cheap these days and they can be an indispensable tool for the mold-busting cannabis connoisseur.

These enable you to get in close, but recognizing mold may require a little practice. Essentially you’ll be looking for filaments called hyphae — the thin branches that resemble mycelium strands. They don’t look like the natural hairs found on the trichomes, and their presence is generally a sign of mold.

How to Avoid Moldy Weed

If you’re consuming cannabis in a legal jurisdiction, then in most cases, the dispensary must — by law — ensure the cannabis they sell undergoes testing for the presence of mold. That said, be aware that certain jurisdictions do not require state-mandated testing for cannabis products. Arizona being one such example.

If purchasing your cannabis on the black market, there is always going to be a risk of mold contamination. But in such instances, several additional factors also come into play. Pesticide residues and the presence of heavy metals can also have detrimental effects on human health. This only adds to the risk of sourcing cannabis from non-regulated sources.

The bottom line is to be aware and stay informed. If all patients begin asking these questions, then the awareness around the dangers of mold exposure will be more widely understood. And that’s something from which we all stand to benefit.

Author avatar

Francis Cassidy
Francis Cassidy is a freelance writer who writes on a variety of topics. With a particular focus on the cannabis industry, he aims to help ensure the smooth reintegration of cannabis back into global culture. When not writing, he's to be found exploring his new base in British Columbia, Canada. You can follow his other works including his photography on his blog

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  1. Mary Jane Kadidlehopper

    Mold article…, rather like telling me someone pointing a gun at my head is a bad thing, but not telling me what to do about it. I guess it’s good to know mold is ruining my crop, but a bummer not bothering to tell me anything about a cure. I’m gonna call it a waste of time article.

    • Jennifer Grant

      Mary Jane (if that is your real name), you should know that there is NOTHING you can do to revive a moldy crop. It’s garbage. There is no remediation. As outlined in the waste-of-time article, you have to DETECT and then pull those plants from the batch. Please don’t ever try to save your cannabis from mold. It could make you very sick. It’s rather like trying to shove your brains back into your skull after the aforementioned gun goes off.