Chris DeWildt

September 15, 2018 4 min read
September 15, 2018
4 min read

How to Grow Cannabis 153 – Introduction to Bud Rot

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In this how-to article, Growers Network explains what bud rot is and how you can prevent it.

The following is an article produced by Growers Network. This article is for educational purposes only. We do not claim any responsibility for any legal or financial repercussions of your decisions. Always consult with a lawyer or attorney before making a decision that could have a legal consequence!

One Rotten Bud to Spoil the Bunch

Hello new grower. Today we’re going to cover a topic that we hope you can avoid rather than deal with, and that topic is a fungus called Botrytis cinerea, commonly referred to as “bud rot” and in other industries is referred to as “gray mold,” and in certain applications of winemaking, a little of this type of rot is actually beneficial.

Do you want to learn how to grow cannabis? Check out Growers Network University!

But we’re not talking about making wine. We’re talking about growing cannabis, and when it comes to cannabis, bud rot is always bad. Understood? Okay, let’s deal with some bud rot!

That old saying about bad apples? It applies to your buds too.

Bud Rot: What is it?

Bud Rot is a fungus that affects the flowers (buds) of your cannabis plant. It begins growing on the stem inside the bud and spreads outward, and as a result it can be very hard to detect. As bud rot grows, it destroys the surrounding bud, eventually producing spores to transmit to nearby buds, turning what remains into slimy mush in the process.

Note: It’s important to note that infected buds are not safe for consumption and should be disposed of immediately.

Meet bud rot. This fungus destroys Cannabis flowers.

How to Prevent Bud Rot

As mentioned above, bud rot is a fungus, so if we control the conditions that allow fungus to thrive, we can greatly reduce the chance of an outbreak. Below is a short list of bud rot’s favorite things:

1. Humidity

  1. Fungi needs a high humidity to thrive. Keep your humidity around or below 50% RH to prevent bud rot.
  2. Remove any standing water that can evaporate and raise the humidity around your plants.
  3. Do not spray any liquid water directly onto your leaves or buds.
  4. Consider a dehumidifier to continuously remove excess moisture from the air.

2. Cool Temperatures

  1. Cool temperatures are an invitation for bud rot, particularly if there’s humidity or excessive water.
  2. Temps should be kept at a minimum of 70 degrees Fahrenheit (21 degrees Celsius) to prevent bud rot.


3. Stagnant Air

Bud rot tends to take hold in environments with very little air flow, and good circulation of air will go a long way toward prevention. Use a fan to generate continuous air flow.

Is Bud Rot Treatable?

Unfortunately there is no treatment to cure bud rot. This is why prevention is so important. If you discover bud rot in your grow operation, you should remove the affected bud(s), being careful not to let the affected buds come into contact with other buds. You may have to remove an entire plant if the bud rot is widespread. Do not shake or otherwise cause the infected portions to vibrate -- doing so may release spores.

Macro view of the fungus Botrytis cinerea or "bud rot"

Well there you have it. Bud rot is serious business. The good news is that you can take steps to prevent it. By controlling the conditions that allow bud rot to develop and spread, you can reduce your chances of an outbreak. Happy growing!

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About the Author

Chris DeWildt is a graduate of Grand Valley State University and Western Kentucky University. He worked in education and publishing for ten years before joining the team at Growers Network.