How To Spot And Prevent Bud Rot/Mould

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How To Spot And Prevent Bud Rot/Mould

No one wants to have to deal with bud rot, but knowing the signs, and how to handle it can help save the vast majority of a plant.

Bud rot is every cannabis grower’s worst nightmare, to have got so close to the finish line, to the only stumble and fall, makes us all die a little inside. However, while it is a harsh lesson, it is a good one, as bud rot is easy to avoid with proper preparation.


Basically, bud rot is a toxic fungal infection that kills and taints the flowers of you cannabis. Once germinated, it is highly contagious, quickly moving from bud site to bud site. Fortunately, bud rot can only set in if the conditions are just right, so it can be quite easy to prevent.

Bud rot tends to affect large densely packed bud, but can be seen across even the loosest of bud sites, especially when growing conditions are wet. You will notice that everything at the bud site (pistils, leaves and buds) start becoming dark and discoloured. They will also start drying up and shrivelling – even though the rest of the plant remains fine.

If caught early enough, you may notice white fluff on the surface of the bud site. This is mould that develops into full-blown rot. It is the first stage of bud rot and means there is still a chance to save some of the plant, as well as prevent others being infected. This can be very hard to catch though, as the fluffy mould doesn’t hang about for long. More than likely, you will see random spots of bud begin to dry out and discolour.

In an advanced stage of bud rot, you may see little black specs in the bud. This is the fungus reproducing. The specks are new spores that are ready to be carried on a breeze to new cannabis plants. Do not breathe it in or allow it anywhere near other plants.


If bud rot has taken hold, then the best (and only) thing you can do is cut away all signs of infection and the area around it. Throw this away and ensure it can never come into contact with any other plant of any kind. You then need to move your cannabis to a warm, dry place with a slight breeze.

From here, you can either harvest your plant as it stands or take a gamble and allow it to ripen.


As mentioned, bud rot is very easy to prevent in healthy cannabis plants, as it needs a certain set of conditions to germinate. It doesn’t matter how many spores your plants come into contact with if the conditions are not right for it to grow and attack. The conditions for germination are as you may expect from a mould. There needs to be:

  • Wet/humid conditions (so watch out after a lot of rain when growing outdoors)
  • Stagnant air/no breeze
  • A cool temperature (anything below 20 degrees Celsius)

So, the best way to prevent bud rot is to make sure these conditions never persist for long, and certainly never at the same time.

When growing outdoors, it can be hard to control such conditions, and the best thing to do is make sure your growing site has a decent breeze and stays warm before you ever put seed to soil. Some outdoor growers will also shake their cannabis plants after the rain to shake out any excess water droplets. Some outdoor growers will even go as far to erect a small frame over their bud that they can throw a tarp over when they know it is going to rain. This will protect the buds from water, but will mean you have to manually water your crop more often. If you decide to do this, make sure that the tarp is supported in the middle. This will allow water to run off the side instead of pooling and potentially collapsing.

Indoors, bud rot should be very easy to prevent, as all of these conditions are easy to control. Just make sure temperatures never drop below 20 degrees, and that you have good ventilation – preventing air stagnation and overly humid conditions.

As a closing note, never use fungicide, neem oil or burn sulphur to try and fix rotting bud. These are not effective against bud rot, and will make the bud you can save taste funny. Some growers try to take preventative measures with specific anti-fungal sprays during vegetative growth, but this can only go so far. The best prevention is controlling the environment to ensure the above criteria never take hold. Never spray bud with anything!

If your rot has got so bad that there is no hope, cut your loss and remove the plant. It is best to get rid of it and minimise the risk of it spreading elsewhere.

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Written by: Zamnesia
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