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How to Prevent and Treat Bud Rot

Written by Ed Rushford May 16 2022

What is bud rot?

Bud Rot, as it is called in the cannabis world, is a slang term for Botrytis bud rot or gray mold that damages cannabis flowers or buds. Bud rot is best defined as a specific form of fungus or mold that grows in cannabis buds. Moreover, most novice cultivators wonder what is bud rot and how does it develop? According to growers, mold begins to form in the centers of the densest buds.

The first infection is seen on the stem inside the bud. Cannabis bud rot is particularly difficult to detect in its early stages. The mold breaks down the surrounding buds after the rot has begun to spread. Mold has an influence on plants, whether they are cultivated indoors or outside. It generates spores, spreading rapidly to neighboring locations in grow rooms and fields. The first visible sign is a wispy white mold. The rot then turns gray, then black. The buds will have a slimy, gooey consistency at this time.

How does bud rot appear under a microscope?

A bud rot under a microscope looks like it is little and light, and it spreads readily in the breeze. Little pocks are produced when the wind blows across these spores in the same manner that flowers release pollen.

Does bud rot smell?

Bud rot smell is distinct. However, it is difficult to detect it due to the zest of cannabis blossoms. You may be able to smell the bud rot up close, and it will smell like any other mold. When you smell it, you’ll know it’s somewhat earthy. However, you do not want to wander about sniffing rotten buds. Breathing in those spores is dangerous to your health, so avoid it. We hope this answers your question about what is bud rot in pot plants.

What causes bud rot?

What causes bud rot cannabis is straightforward. The main answer to the question “what causes bud rot” is a form of mold that destroys developing buds in high humidity settings. Most of the time, moisture is retained by thick plants and big buds, resulting in excess wetness. Cannabis bud rot is a bigger problem for outdoor producers since it is challenging to manage the climate. Cannabis bud rot can occur if the humidity, ventilation, lighting, and temperature in indoor grow rooms are not correctly controlled.

It is evident that morning dew and rain levels cannot be controlled for outdoor crops. This implies that plants can become saturated at any time of day or night. Outdoor producers, particularly those in coastal settings, must grasp the best methods how to prevent bud rot cannabis. This is a serious challenge because of the difficulties in managing humidity levels. Because there is insufficient air circulation around the plants, dense plants and bigger buds are usually damaged. Botrytis mold spores may be found anywhere; however, they can only harm your plants under conditions such as high humidity, stagnant air, and extreme temperatures.

Diagnosing bud rot

What does bud rot look like?

Most newbie cultivators wonder, “what does bud rot look like and how does bud rot smell.” The initial cannabis bud rot signs come when the mold attacks the plant’s stems, resulting in a mushy grey hue. As Botrytis spreads, the leaves get yellow, wilted, and burned. Because rot begins inside the buds before spreading to the exterior parts, diligent and regular monitoring is required to catch the early signs of bud rot before it seriously harms your plants. And to answer your question about what does bud rot look like, here are some bud rot signs:

  • The stems have a mushy gray appearance.
  • Leaves that are yellow, withered, or burned
  • Fluffy white fungus on buds
  • Spots that form on the leaves
  • Leaves that are brown, dried, or curled
  • Leaf development that is deformed or irregular
  • Calyces are grayish-brown.
  • Leaf coloring that is darker or purple
  • Minor black spots
  • Brown blooms that have rotted

After identifying bud rot signs, change your clothes before moving to another grow room or region. It is suggested that you wear a protective suit. Identifying bud rot on crevices and cracks of any flowers suspected of having a fungus is crucial. Examine the core to determine if there is any decay. If the core has a mushy brown color, remove the plant, store it in a bag, and keep it away from the rest of your plants to avoid infection. Examine additional plants for similar early signs of bud rot, and quarantine them. Keep an eye out for the formation of a dusty gray webbing with white spores. Pollinators, water, and wind all help spores spread outside. Spores are tough to regulate, even in indoor grow facilities.

What does Botrytis do to cannabis plants?

When Botrytis infects a bud, the bud begins to die. It won’t be long until the bud loses its brilliant color and starts to appear lifeless and rotting. The latter stages of Botrytis are more easily identified. But by then, the bud rot would have spread and expanded. You must be able to detect Botrytis as soon as possible. Once cannabis bud rot has taken hold of the plant, the buds might occasionally seem practically identical on the outside at first, but they generally start withering in areas. The region will frequently dry up and easily peel apart. Buds’ insides might become brown, gray, or even purple. Cannabis bud rot might seem different depending on the life stage or type of mold or fungi.

  • Fluffy and white
  • Brown or dark gray (sometimes even dark purple)
  • The buds might be covered with black speckled dust that readily blows away (fungus spores)

Preventing bud rot

The easiest strategy on how to prevent bud rot is to combine optimum growth conditions with proper plant upkeep. Dried bud rot flourishes in growing rooms with high humidity, poor ventilation, and somewhat warmer temperatures, and it might be more challenging to get if your plant is bushy, has thick buds, or has weak genetics. We may argue that how to stop Botrytis begins by picking the ideal genetics for your growing environment. Always search for very robust plants, and if you can’t provide them with ideal growth circumstances, grow Sativa-dominant plants.

Mold on the cannabis plant
White mold on the plant cannabis


Pruning and training crops can also aid in how to stop bud rot. Airflow increases and moisture accumulation is reduced when plants are pruned efficiently. You may also use trellis or Scrog to help your plants extend their branches.

Watering and feeding appropriately 

Plants with strong immune systems are better able to resist mold development. Growing organically with various nutrients helps boost beneficial microorganisms in the soil and maintain plant immune systems healthy and ready to combat illnesses. Above all, preventing plants from excessive moisture is critical in the fight against Botrytis cannabis. Watering plants in the morning can also help reduce humidity in the garden after the sun has set or when the lights are turned off later in the day; thus, dried bud rot prevention.

Spacing plants further apart

Cramming a large number of plants with many buds into a compact space might increase the likelihood of Botrytis. Buds should never be in contact with one another. You should not touch cannabis plants, and air should be allowed to circulate freely between and around all areas of the plant. Making sure that each large bud gets a little “breathing area” to itself is another way of preventing bud rot.

Adjusting humidity 

Another way of preventing Botrytis is by using dehumidifiers to remove excess moisture from the air, lowering the risk of mold and mildew growth.

Add or adjust ventilation

Producers should also let air circulate within the plant and over the buds and leaves as a way of bud rot prevention. Fans are beneficial inside, primarily if you use an exhaust fan to direct hot, humid air away from your plants. Outdoor gardeners can relocate potted plants to a cooler spot, but there isn’t much you can do to promote air circulation if the plants are in the ground.

How fast does bud rot spread?

After identifying bud roots in your plants, most producers usually wonder how fast does bud rot spread in their grow. To answer the question, cannabis bud rot spreads fast and is exceedingly infectious. Both indoor and outdoor crops can become completely diseased in days. As a result, you must take Botrytis prevention steps like using bud rot prevention spray and treat your plants as soon as the first indication of infection appears to avoid mold from spreading to your other plants. These measures are essential to solving your curiosity about how fast does bud rot spread in cannabis plants.

How to prevent bud rot outdoors?

How to prevent bud rot outdoors is similar to stopping it indoors, with a few slight variances. To begin to prevent Botrytis outdoors, use a fungicide (ideally organic) until the infestation is under control, then spray once a week as a preventative measure. As you may be aware while growing outdoors, you are at the whim of nature, and weather can induce Botrytis. Thus, it is strongly advised to construct an improvised structure (same as a greenhouse) to shelter your plants from rain, especially if they are already infected.

If you find cannabis bud rot on any of your outside plants, remember to remove the affected sections and dispose of them in a sealed bag to prevent the spores from spreading. Also, maintain diseased plants separate from healthy plants in a dry, cool environment with ample airflow, and do not return them to the original location to guarantee your plants remain healthy until harvest.

Salvaging bud rot – is it possible?

It’s critical salvaging bud rot as soon as you see them. When even a single bud begins to exhibit indications of gray mold, the rot can spread to the remainder of the cola and other buds on the plant. If the triggering conditions (lack of ventilation, moisture) do not change, a single site of infection can soon damage a whole plant’s crop. Avoid salvaging Botrytis by using sprays or fungicides like Neem oil or sulfur when your plants are in bloom since these treatments will alter the buds look.

Removal of bud rot cannabis

Remove any rotten portions and surrounding regions as soon as possible. The only method used when salvaging bud rot is to remove any mold from the plant and then relocate it to a cool, dry location with a pleasant wind. Also, take special care not to allow any dried bud rot to affect the remainder of your plant. This is how to get rid of bud rot. What will happen next? You may either harvest the cannabis plant now or let it develop further, but only if the atmosphere is improved. If your plant develops bud rot cannabis, it indicates that it needs less wetness and drier air. You can leave the plant to continue ripening after removing the diseased buds if you can enhance the environment. However, if the environment is not corrected, it will generally return, occasionally attacking other buds overnight. 

What’s the difference between bud rot and powdery mildew?

Millions of growers worldwide are devastated by Botrytis and powdery mildew just as they are about to harvest, even though these diseases may hit cannabis plants. The vulnerability of a garden to disease is frequently linked to environmental factors like temperature, moisture, light, airflow, pH, and nutrients. Fungus flourishes in the presence of enough moisture, warmth, acidic conditions, and a consistent source of food.

Powdery mildew is uncommon among fungi, and managing it can be difficult for commercial cannabis farmers. Unlike Botrytis, powdery mildew cannot be avoided by merely drying off the environment. Powdery mildew is sometimes referred to as a dry mold by growers because it spreads quickly in situations with low humidity levels. Powdery mildew spores do not need standing water to germinate; only brief periods of high humidity are required. A brief change in the environment is all that is needed for spores to spring to life, hook onto the leaf surface, and begin draining energy from the plant.

Bud rot vs Root rot

Root rot is a significant problem that can destroy a cannabis plant. Roots form a network that collects and transports water, oxygen, and nutrients to the rest of the developing plant. When plants are overwatered and lack adequate drainage, their roots effectively drown, cannot absorb oxygen, and begin to die. A cannabis plant will not grow correctly if its roots do not form. Underwatering cannabis plants can also lead to root rot. To take in oxygen, healthy roots require a balance of water and time to dry out. Root rot is difficult to treat and results in nutrient-deficient and stunted plants. If the plant gets root rot, you will undoubtedly have to discard it.

Ed Rushford

Ed Rushford’s impact on cannabis growing is undeniable. Though he tends to focus primarily on 2 areas, plant training techniques and dealing with disease, pests, and other problems, he has offered many insights into how cannabis plants live and grow. That’s not to say that Ed is unfamiliar with the complete life cycle of cannabis, from seed to harvest, but he uses his widespread knowledge to hone in on the minutia and niche areas of growing cannabis. Ed’s goal is to spread knowledge and allow for everyone to become better growers. About this Author

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