Even the most skilled and experienced of cannabis growers who keeps their grow op immaculately clean will eventually run into a mold problem. Indeed, mold happens to be a common complication when it comes to caring for your crop. And while it doesn’t necessarily mean your marijuana is ruined, it can be annoying to remedy, so you want to keep on top of it as much as you can. How can you spot it? How do you treat it? More importantly, what can you do to prevent it from happening again?
Signs That Bud Rot Is Attacking Your Cannabis
While there are a variety of mold and mildew issues that can occur, the two most likely culprits that the average cannabis grower will face are botrytis (a.k.a bud rot) and powdery mildew.
Bud rot sets in at the base of the plant stem, which can make it difficult to spot right away. Keep an eye out to see if the leaves surrounding your colas (i.e., the cluster of buds that grow tightly together) become withered, discolored or dried out. If you spot those warning signs, look closer to see if any of your buds have white, gray or blue-green fluff growing among them. This can cause your flower to dry out completely and crumble (if you have low humidity) or turn sludge-like (if there’s high humidity).
As bud rot worsens, you’ll notice black spots in the mold. These are mold spores that can easily spread to other plants, thus ruining an entire crop. These spores are also unhealthy for you to inhale — so wear a mask and do not breathe them in if you spot them on your plants. However, if you’re checking your plants regularly, you should be able to catch the rot before it gets to this stage.
How To Spot Powdery Mildew On Your Cannabis Crop
Powdery mildew, on the other hand, looks exactly like it sounds. You’ll be able to spot it on the leaves of your plant first, looking like a fine coating of baby powder. If not treated, it will spread from the leaves to the rest of the plant. The powder prohibits photosynthesis, and if left untreated, will cause your plants to yellow, wither away, and eventually die. Like bud rot, if powdery mildew is left to spread, it will produce dangerous black mold spores that can easily spread to other plants.
There are three different things that together create the perfect environment for these types of molds to form:
- Stagnant air
- Cool temperatures
- Excess moisture and humidity
Mold thrives in areas that are dank and damp, so do your best to mitigate those conditions, which is a lot easier for indoor growers to do. Keep your temps above 68 degrees Fahrenheit to avoid it being too cool. You should also be able to control your humidity levels with the proper ventilation, which will help prevent stagnant air.

Powdery mildew spores are airborne and can be easily spread through the air from one plant to another.
What To Do If Your Cannabis Crop Succumbs To Mold
However, mold can creep in even if you do your best to prevent it. If your plants do succumb to either bud rot or powdery mildew, there are a number of things you can do.
First, decide if the plants are too far gone enough to save. If you haven’t been as observant and are already seeing black spores, it may be time to bite the bullet and end those contaminated plants to start your grow op from scratch. However, if you catch mold at the starting stages, there is hope. First of all, make sure that all three elements — temperature, humidity and air flow — are at the correct levels before pressing on.
There are commercial products you can purchase to combat bud rot and powdery mildew, or you can whip up some proven homemade remedies. If you’re able to completely move the infected plants away from healthy ones, then that’s a good place to start.
For bud rot, a commercial product is most likely the way to go to ensure it’s fully taken care of. When it comes to powdery mildew, you can spray it with fungicides, but remember that you’ll likely be consuming what you’re spraying, so you have to ensure buds are appropriately flushed before harvest.
If you don’t wish to foliar spray with fungicides, there are alternative, nontoxic treatments, like a cider vinegar/water mixture. Other home remedies include a mixture of baking soda, water and dish soap. However, if neither of these are strong enough for your plants, then you may want to consider a commercial-strength product.
When you find a telltale ruined leaf that indicates bud rot, it’s a good idea to turn your grow-op fans off before cutting the affected branch from your crop. Next, swab the cut section with isopropyl alcohol (as well as your cutting tool, so as to discourage cross-contamination). However, often is the case that cutting off buds afflicted with bud rot will not be enough.
Salvage damaged cannabis flower by placing it in a clear alcohol, such as gin or vodka, which will extract THC from the buds and eliminate the mold.
And of course, once your crop is mold free, continue to keep a vigilant eye on your plants and work on maintaining as balanced a grow environment as possible to ensure your cannabis stays mold free.