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Microbial Risks in the Hobby Grow w/ Dr. Tess Eidem
How Cannabis Hobby Growers Can Better Manage Microbial Activity (TYM)
If you read my last piece summarizing Dr. Tess Eidem’s presentation on microbiological risks in cannabis (aka the disgusting truth about legal weed), then you' may have asked yourself:
How does my home grown weed compare to commercial cannabis?
Is the weed I’m growing at home safer?
How do I know? How can I know more?
I was in the same boat, which is why I reached out to Dr. Eidem in hopes of some more insight, and she was gracious enough to grant me an hour of her time to answer these questions and discuss these challenges that growers and consumer face in more detail.
By the time you reach the end of this piece, you will understand:
Common sources of microbial contamination
How home grown cannabis compares—in both process and Total Yeast and Mold (TYM)—to commercially grown cannabis, and
Ways to monitor microbial levels in your home grow.
Plus, if you don’t grow, you might even be scared into considering it (if you weren’t already).
Ok, let’s dive in…
If you’ve only got a few minutes, here’s the 5 key takeaways you’ll want to know:
Generally speaking, home grows can be (and often are) cleaner (as it relates to TYM) than commercial grows. Lots of variables in here, but smaller grows typically benefit from less contamination, workers, and opportunities for issues.
The most common causes of micro risks are contamination from grow supplies, shared genetics, or mechanical transfer (clothes, shoes, etc.). Cleanliness surrounding the grow makes a big difference.
Build a MicroLab to test crops onsite. This was Dr. Eidem’s top recommendation for those serious about managing their microbial levels (as a hobby grower or as a commercial facility) and can be done in a small setting for ~$1000, up to a few thousand for more advanced commercial needs.
Vet your processes. Specifically, Dr. Eidem stresses the importance of backing up claims and processes with actual data, especially when it comes to TYM management. This holds true for everything we do; how do you know it works unless you’re measuring how well it works?
Bonus: Poorly written laws (and not poorly grown weed) are a big part of the remediation problem. Remediation is controversial in this space, and while many growers like myself like to sit on the pedestal of “You shouldn’t have to remediate properly grown weed,” there are markets whose regulations are impossibly restrictive, making it so that even the cleanest grows with only a natural biome would still fail TYM testing without remediation.
A bit of background…
I was first introduced to Dr. Eidem and her work ont he microbial risks in cannabis through LinkedIn
While her work overlaps with cannabis, she is the first to remind that she’s a “microbiologist, not a cannabis researcher”
As a Colorado resident, she exercises her legal right to cultivate each year, planting a small amount of plants outdoor in her garden
As a microbiologist, there’s a few suggestions that she made that may seem simple if you’ve got the tools and know-how, but complex or daunting to the average grower that can’t remember middle-school biology (I fall in that latter category). Don’t let these overwhelm you; keep this on hand as your knowledge and skillset increases.
Let’s begin with a brief story:
Dr. Tess Eidem, a degreed microbiologist with a hyper-focus on cleanliness of cannabis who is also a small-scale hobby grower.
Dr. Eidem grows her cannabis outdoors—exposed to all of the elements and natural microbiological activity, good and bad, that nature throws at it.
She then dries in her garage, a (mostly) uncontrolled space.
In spite of these conditions, when she tested her harvests for TYM, the results came in at ~1500 CFU (colony-forming unit; standard measure of biological activity).
For reference, Colorado’s acceptable limit is 10,000 CFU. Some markets allow 100,000 CFU. Others, like New York, allow 200 CFU.
Said differently, commercial cannabis can have upwards of 6x TYM as Dr. Eidem’s in Colorado’s legal market.
Even scarier: There are grows that are having a hard time coming in under that limit (which is where remediation comes in).
In her words:
"I grew 4 plants last year. I tested it. I took samples of all my flowers...and I tested for total yeast and mold, which is a simple dilution. So you grind up your flower, you weigh it out, and you take dilutions of that because there's a lot of microbes on there."
"When I did it at home, 1500 CFU of total Yeast and Mold, and I didn't have antibiotics at my place either, so that's a pretty low number. Most states like Colorado, where I am, it's 10,000 CFU. Some states, that’s the limit. That's the threshold. Once you go above that, it's considered contaminated. Some states it's 100,000."
"By the time you start seeing visible mold, then you are probably in the millions of CFU. But you do start to see quality differences around 100,000."
"I dry cured in my garage—which is not like the most sanitary of environments‚ and I was still able to, with only four plants, hit that low of a TYM count."
Where do these microbiological risks & threats come from in cannabis?
Grow Supplies: Substrates, risers, saucers, trays, tubing, etc.
Genetics: Contaminated genetics as well as problem-prone genetics that have low resistance to threats.
Workers: You, the grower, are bringing it in. Can be on your clothes, shoes, in your hair, or anything you came into contact with an brought into your grow.
Scale: Too big, too many plants, not enough spacing. This is especially true in outdoor crops where plants don’t have enough “elbow room” between them.
And these problems can pop up post-harvest in Dry and Cure spaces as well if growers aren’t mindful.
“If home growers are having problems, if they have visible mold on their harvested products, it's only going to get worse in dry and cure.
So, there is something to be said about…[really having] control. Try to be really good to your plants so that they aren't stressed, so that they have everything that they need.
[Additionally] Co-infections like we talked about with hop latent viroid (HLVd) can also predispose [plant material] for other microbial pathogens to come in and start taking over."
Of particular importance: Dr. Eidem mentioned that many substrates come packed full of microbial activity (good or bad).
If you aren’t cleaning your substrates, you are likely introducing a variety of microorganisms to your efforts, so cleaning (and vetting the source of the substrate) are crucial to mitigating unwanted micro risks.
How can you test your weed for TYM?
Microscope & Plates (at home/on-site)
Immunostrips (similar to a rapid covid or pregnancy test)
Speciation (mail-in and 3rd party testing)
According to Dr. Eidem, the best way to manage your TYM throughout the growing and post-harvest process is by building out your own microlab.
Now, here’s where I said that might sound overwhelming because I, too, was overwhelmed by the idea of reaching deep down into my THC-laden brain for any glimmer of insight into middle school biology and coming up short.
You don’t have to be a rocket scientist to do these types of testing at home, but you do need the right equipment.
Dr. Eidem likened it to the ability to brew beer at home or culture mushrooms for cultivation, both of which can be done at home with the right attention to detail and sterility.
When pressed, she seemed to think it was possible to build a small microlab for a few hundred dollars, but said that shooting for $1000 was more reasonable based on her experience (and the trade-off in advance onsite testing if you’re a commercial facility was a no-brainer).
I could honestly have written an entire piece on building out a microlab for the Hobby Grower (and maybe I can talk to Dr. Eidem into a co-authored piece in the future), but, in the meantime, here’s the list she gave me of what a small lab should include:
Butane Burner (Flame)
Loop - for gathering single colonies
Micrscope - for identification
Micro Pipettes - distirbuting small volumes
Tips for Pipettes
Pressure Cooker (Instant Pot) to autoclave; Autoclave is for sterilizing
Sanitize vs sterilize: sterile means you killed everything
Sterilize tools, plastics, metals as well as your own media (for plates and cultures)
Approximate Microlab Startup Budget $200-1000
“For everyday growers I really think that having a little internal microlab—which I've helped a couple of cultivators get up and running—can be just so valuable for folks, because you can't see microbes. You cannot see them no matter how hard you look until they're in the millions or billions of cfu. And at that point you are too far gone.
So you need to be able to monitor and manage something that you can't see with your eye, which means you need to bring in other tools to be able to monitor and manage those."
You could do it for a couple of hundred [dollars] if you really wanted. Like pipets and everything. Earlier this year. I got microlab up and running for a cultivator out on the East Coast, and it cost a little under $1,000 to get everything. So, for a commercial operation, that's a pretty cheap investment to get an idea [ahead of testing]…
“We were spending like $20,000 every other week when I was at Columbia Care. So it was not cheap to do all that testing."
Process Validation & Process Preventative Control: The Missing Piece
One of Dr. Eidem’s biggest concerns about the space is that there’s rarely data to back up what’s being said and done.
I even encountered this in my prep for our interview and this article:
People are using Freeze Dryers (lyophilization) to “remediate” material
People are using UV in the grow to “kill” microbial problems
People are doing sprays and dunks to “sanitize” crops before testing
People are doing BHO extractions to “kill” contaminants
But most of these “people” don’t have any data to confirm their processes are working beyond a Pass or Fail in regards to compliance testing.
Meaning, the people who have told me that freeze drying their harvests results in a remediated (reduced TYM) final product are not backing that claim up with:
Air Dried TYM vs Freeze Dried TYM counts from the same batch
TYM at Harvest vs TYM after Lyophilization
And this lack of data also leads to conflation of use.
For example, I asked Dr. Eidem about the role a freeze dryer could play in managing safe TYM levels for a hobby grower without access to complex lab testing and expensive remediation processes.
Her response: Sure, a freeze dryer could potentially remove some microorganisms, but lyophilization as a process is used to preserve these compounds for research, the opposite of what you’d want if trying to reduce your TYM. More likley however is that the process itself is less susceptible to contamination that could occur during air drying.
"What [freeze drying] really does, though, is it cuts out a big chunk of the process that is very prone to microbial contamination, which is that dry cure phase because you're not going through 10-20 days of drying and curing depending on your process. You're going through a day of putting it in a freeze dryer.”
Whatever you are doing, measure your efforts so you know if it is working or not. And then compare those notes with the industry and related industries to establish best practices and processes.
Which brings me to…
When Regulations Force Remediation: A Cautionary Tale
Before I leave you, I wanted to double-down on the point I made above regarding remediation and its use.
As I mentioned, I’m often of the opinion that properly grown cannabis should not have to be remediated. And I believe that this is a stance that Dr. Eidem believes to be true as well given her experience growing outdoors and drying in her garage.
There’s 1 (massive) exception: When laws get in the way.
If you’re familiar at all with the cannabis industry, you’re likely not surprised that, yet again, regulators with little knowledge of cannabis and its cultivation have written rules and laws that make little sense (and create impossible barriers for producers).
New York’s 200 CFU limit for TYM probably sounded good on paper.
The regulators might have looked around at other markets and said, “Gee goly, 10,000 seems high, 100,000 seems extreme, let’s go super strict. How’s 200?"
And they all nodded and murmured and it became law.
But that limit doesn’t account for the natural biome (biological activity) of a plant, which can often exceed 200 CFU according to Dr. Eidem, even in the best conditions.
Put simply: You can grow the perfect plant in NY and still have to remediate it to comply with testing limits.
This forces producers, even those committed to the highest quality standards, to consider options like remediation—that aren’t approved for other consumable crops—when they shouldn’t have to.
How To Use This Information:
Research your market. Look up what the allowable limits are for TYM in your area and if your market is on either extreme of the spectrum (from 200 cfu in NY to 100s of 1000s elsewhere), consider growing your own.
If you’re a commercial producer, consider building a MicroLab and/or buying an ATP meter for swabbing and sampling, helping validate your internal processes with actual data.
If you’re a hobby grower, focus on cleanliness first, and, if you’ve got the budget, interest, or concern to justify it, build out a small MicroLab of your own, with more budget-friendly supplies.
I’ll leave you with my favorite quote from our call:
"I find that most hobby growers are home growers. They're so proud of their products.
And when you have a bad batch and you have to kill some plants or cold them out of your garden. It's sad. It's really sad. I've had to do it, but it's better to do it and protect the rest of your plants."
Want to hear the whole conversation?
Dr. Eidem gave me permission to share the full recording with those of you that are interested. It’s just under an hour long, but if you’d like to listen to it on your drive to or from the grow, or while you’re working in the grow, reply to this email and I’ll send you the link.