How to Identify And Prevent Bud Rot: Practical Tips

Whether you are reading about bud rot for the first time or looking to update your knowledge about this frustrating weed plant problem, this blog offers deep insights into identifying and preventing bud rot among indoor weed plants. 

What is Bud Rot?

Bud rot or gray mold is a mold type that develops in the buds of weed plants, causing the buds to rot from the inside out. It is often caused by a fungus called Botrytis cinerea, hence the name botrytis. This necrotrophic fungus also affects different plants and plant parts, including fruits, petals, flowers, stems, and leaves.  

The infection starts from the stems on the inside of the buds before spreading to the outside. Thus, it is difficult to detect the presence of mold in the early stages. Detection only becomes easier when the rod starts spreading in different directions, producing spores that spread to other nearby plants in the growing area. 

The earliest indications of a bud rot attack on an indoor plant include a mushy and gray stem. This progresses into wilted, burnt, yellow leaves. A closer look at the cracks and crevices of the affected buts often reveals the presence of a rotting bud with a brown and soggy core. Other symptoms include;

  • spots on leaves
  • curled, dry, brown leaves
  • purple colored or dark leaves
  • greyish-brown calyces
  • abnormal leaf growth


What Causes Bud Rot in Weed?

Having established what bud rots are and how to spot them, let’s look at the common causes.

1. High Humidity Levels

The most common and significant cause of bud rot is high humidity levels in the grow area. A high humidity level (above 60%) means water will condense on surfaces around, including the plants. The density of the buds of weed plants makes them the ideal spots for trapped water. This water condenses inside the buds, creating an enabling environment for the gray mold to grow. That is why experts recommend not leaving buds in humid or moist air for a long period. 


2. Inadequate Ventilation

Poor ventilation is a problem peculiar to indoor growers and indoor plants. Once there is no adequate air circulation underneath, above, and through the plant’s insides, the resulting environment allows bud rot to thrive. In addition, the absence of proper ventilation will increase the chances of moisture getting trapped between the leaves of the weed plants. Then humid air pockets develop, stimulating the growth of the gray mold. 


3. Too High or Low Temperatures

Exposure of indoor weed plants to the wrong temperature is another major cause of bud rot weed. Anything short of the perfect temperature condition (or below 68 degrees Fahrenheit) will give room for fungus and mold to thrive. Mold, including gray mold, grow faster in warmer temperatures, especially when combined with increasing relative humidity. 


4. Dense Foliage and Buds

A downside of dense foliage is its high likelihood of trapping too much moisture, especially around the stems and buds of your indoor weed plants. This is more likely to happen in crowded grow areas where plants are crammed too close together. As mentioned above, enclosing moisture in any part of your plant will only create an enabling environment for the growing Botrytis cinerea fungus. 


 5. Plant Genetics and Immune System

Genetics contributes to the health of plants. That is why some strains will be more susceptible to bud rot than others. For instance, strains structurally adapted to warmer, humid climates will be more mold-resistant due to their longer, lighter, and wispier buds. However, those from drier climates will be more susceptible to the attack of gray mold once the environment becomes humid.  


How To Prevent Bud Rot In Indoor Plants?

One upside of indoor growing is that you can control your growing environment. Since we have established that most of the causes of bud rot in weed plants are associated with the environment, growers can modify their grow area to ensure it doesn’t support the growth of gray mold and, by extension, bud rot. 

1. Keep your buds dry. 

Keeping your buds dry is the most effective way of preventing bud rot. However, your buds can only stay dry if the growing environment is not damp or overly humid for an extended period. Experts recommend 40-50% relative humidity for the flowering stage of your indoor weed plants. 

how to prevent bud rot


2. Ensure optimal airflow. 

Adequate air circulation means air moves over the leaves and through the dense buds. Consider introducing inline induct fans and clip-on fans to achieve excellent air circulation and vent hot, humid air out of your grow area. You should also adopt a free spacing arrangement that ensures free airflow.

how to prevent bud rot


3. Set the ideal temperature.

Temperature can play a crucial role during the flowering stage. To prevent bud rot in indoor plants, it is best to maintain a temperature of around 24°C (75°F) during the flowering stage. It is the ideal middle-ground for the surrounding temperature. =


4. Trim bushy plants and space them properly. 

Bushy plants lead to dense foliage and buds. When you defoliate these overly bushy plants, you can effectively lower the humidity around and through your indoor plants. It is best to remove the leaves that are not getting sufficient light, usually at the bottom and middle of the plants. 


5. Choose the right strain

Choosing the right strain solves the genetics and immunity problems associated with bud rot. For example, Sativas are adapted to humid equatorial regions. Their airy, wispy light buds are less dense, allowing adequate airflow. Therefore, they are more resistant to gray mold. Conversely, indicas are more adapted to dry mountainous regions, and their buds are denser. Consequently, they will be susceptible to mold, especially in a humid climate. 



Like other plant diseases, even the most experienced grower may find bud rot weed a formidable adversary to their successful grow and harvest. The only way to win the battle is to understand the causes and the suitable preventive measures to take, and we are confident this blog has equipped you with this essential information. 

At Mars Hydro, we offer efficient grow room accessories that help to create and maintain an optimal environment that prevents bud rot. From smart inline duct fans and carbon filter combos to clip-on fans and ducts, we have all you need to achieve the best ventilation for your indoor weed plants. 

Good luck.