Bud Rot

After months of painstaking attention, electricity bills, sleepless nights, and labor – these two words are the last thing any cannabis cultivator wants to hear.

Harvest time is meant to be a landmark moment that’s celebrated with trimming parties and a well-deserved pat-on-the-back.

However, bud rot is a stealthy mold that’s primed to ruin months of work in an instant. Read along to understand what bud rot is, what causes it, and how to stop bud rot from destroying your cannabis garden.

Picture of Roy Stevens
Written By Roy Stevens
Image used in bud rot guide

Table of Contents

What is Bud Rot?

Bud rot, such as botrytis, is a parasitic fungus that’s been documented extensively due to the damage it incurs on the agricultural industry yearly.

Once a plant or flower is infected with bud rot, dark and fuzzy mycelium patches become visible. These grey fuzzy patches are due to the branching conidiophores that cluster together to create a single conidia.

Conidia is the scientific word for the structure of the spore. Botrytis reproduces asexually, which means that its spores can grow into new individuals without any sexual interaction.

Once a cannabis flower is infected with bud rot, spores are immediately released throughout the grow room – ready to wreak havoc on your precious trichome-covered flowers.

A single instance of botrytis can unleash hundreds of thousands of spores in a given moment. When it comes to fungus – their power lies in their sheer number.

So, if you were wondering, “what does bud rot look like?”, look no further than dark grey fuzz that typically appears on the cannabis flower; however, it can also be found on the stems and leaves.

Also known as a “blight,” you will immediately recognize the dark spots that will begin to spread on your cannabis crop.

Due to its parasitic nature, bud rot relies on its extreme ability to propagate spores to new hosts. Botrytis depletes plant material of all of its nutrients, which pushes the plant into a deeply weakened state.

What Causes Bud Rot?

There are three primary causes of bud rot you should aim to avoid –

  • High humidity
  • Lack of airflow
  • Unsanitary conditions in the grow room

High humidity is the bane of all cannabis cultivators. A single night that exceeds normal humidity levels can ruin your entire harvest, which is why it’s an absolute must to utilize environmental controls.

When it comes to growing cannabis, high humidity is classified as anything over 50% RH. This is especially true when your cannabis crop is flowering and most vulnerable.

When the humidity exceeds the 50% threshold, condensation occurs within the room. It’s within this condensation that bud rot spores spring to life.

Lack of airflow is another primary cause of bud rot because it enables high humidity. This means that a lack of airflow is also responsible for increased condensation, which provides the perfect environment for bud rot to flourish.

Lastly, unsanitary conditions in the grow room should be a significant concern because botrytis spores thrive in dirty grow rooms. Spilt water in a corner, dead leaves left to rot, and moist soil that fell on the ground are all perfect environments for bud rot.

Bud rot spores are found in nature among trees, bushes, and flowers; which means you can easily bring in a single spore on your clothing into your grow room.

Once inside the grow room, bud rot may lie dormant until a lack of airflow and increased humidity give it the ingredients for life.

How to Prevent Bud Rot During Growth & Flowering Stages

Here’s the good news – bud rot can be prevented.

When it comes to anything in life, preventative measures always trump reactionary techniques, and this is especially true for managing the well-being of your cannabis garden.

Whether you want to learn how to prevent bud rot outdoors or indoors – these tips are essential for beginners and professionals alike.

Control Humidity Levels

Bud rot flourishes in temperatures of 32 to 80℉. Although research shows that bud rot slows down during cold temperatures, humidity is the primary driving factor.

Dry and hot environments are impossible for bud rot to flourish; however, your cannabis plants won’t thrive in this environment as well.

This is why you must find the proper balance within your grow room that satisfies your plants and keeps any possibility of bud rot at bay. It’s recommended to keep the grow room between 75-85℉ and a maximum of 40% RH at all times – whatever the cost.

Keep Your Cannabis Plants Healthy

When your cannabis plants are healthy, they are less likely to be attacked by bud rot. Botrytis, for instance, preys on plants that have a weak immune system. Therefore, it’s essential that you keep your plants healthy and happy.

Keeping your cannabis plants healthy entails proper environmental conditions, watering schedules, and nutrient levels. When one of these aspects isn’t ideal, your cannabis plant becomes vulnerable to spores of bud rot.

Prune Your Cannabis Plants

Cannabis plants are fast growers that produce a lot of greenery. Pruning your cannabis plants is essential to allow improved air circulation throughout the body of the plant.

One of the best methods for pruning cannabis plants is to remove all branches that are near the bottom of the plant. Starting from the base of the plant, the lowest 8-24 inches (depending on the overall size) should be completely removed.

Pruning has a large impact because it also allows you to easily irrigate and inspect your cannabis crop. Your cannabis plants are less likely to develop bud rot when you keep your cannabis plants organized by pruning.

Other Proven Methods to Keep Your Cannabis Plants Free of Bud Rot:

  • Keep Your Grow Room Clean
  • Decrease Humidity For Dense Flowers
  • Increase Ventilation in the Grow Room
  • Use Oscillating Fans That Blow Across the Canopy
  • Water Management

How to Prevent Bud Rot Post Harvest

Once you’ve completed a successful harvest, it’s essential that you prevent bud rot from forming on your fresh cannabis buds. This is done by regulating the temperature and humidity in the drying room.

The humidity of 38-43%, along with 70-80℉ is the optimal range for drying cannabis flowers. Ventilation is also crucial to keep fresh cannabis buds from suffering an attack from bud rot.

Other tips include:

  • Never stack cannabis flowers on top of each other
  • Rotate the flowers each day for inspection and to ensure flowers aren’t touching each other
  • Use a hygrometer/thermometer combination to continuously monitor RH and temperature

By understanding the basics of bud rot, you’re empowered to keep your grow room bud rot free. We advocate preventative measures because there isn’t a cure for bud rot. Bud rot is systemic, which means once a plant has it – it has it for life.

This also means that once cannabis is infected, you’ll need to carefully quarantine the plant and dispose of it far from your grow room. Although fungicides do exist, they are merely a band aid – not a cure.

Humidity, temperature, and airflow are the three factors that will keep your cannabis grow room free from bud rot. Looking over each of these factors will help you prevent a frustrating and costly experience.

Have you ever experienced bud rot? Join in on the conversation at The Highest Crop and tell us what you did to bring your cannabis garden back to life.

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