Problem Identifier / How to Stop Bud Rot

What is Bud Rot?

Bud Rot, as known in the cannabis industry, is a slang name for Botrytis or gray mold that affects cannabis flower – commonly referred to as buds.

The question of what bud rot is can best be answered as a specific type of fungus or mold developing in cannabis buds. Growers see mold beginning to grow in the cores of the densest buds. The initial infection is located on the stem on the inside of the bud. Cannabis bud rot is extremely difficult to see when in the beginning stages. Once the rot has started to spread, the surrounding buds are broken down by the mold.

Mold impacts plants whether they are grown indoors or outdoors. It produces spores that are easily spread to other areas in both grow rooms and fields. The first noticeable symptom is a wispy white mold. Then, the rot turns gray, then black. At this point, the buds will take on a slimy, mushy consistency.

If bud rot is discovered early, you can take action to prevent further damage. If you are successful, your plants will recover and continue to grow without issue. Once a mold infection becomes too severe, you could lose your crop entirely. If you see the growth of mold, immediate action is critical.

Cannabis Bud Rot
Thorough and frequent examination of plants is recommended to catch bud rot early.

What Does Bud Rot Look Like?

The symptoms of mold include:

  • Mushy grayish coloration of stems
  • Yellow, wilted and burnt leaves
  • Visible signs of mold
  • White fluffy fungus on the buds
  • Spots appearing on the leaves
  • Brown, dry or curled leaves
  • Deformed or abnormal leaf growth
  • Greyish-brown calyces
  • Darker or purple coloration of the leaves
  • Small black spots
  • Rotten brown buds

The first symptom appears when the stems of the plant are attacked by the mold resulting in a mushy grayish coloration. As bud rot progresses, leaves take on a yellow, wilted and burnt appearance. Since rot initially forms inside of the buds prior to moving to the outer areas, careful and regular inspection is necessary to catch the fungus before it can do major damage to your plants.

Thoroughly examine the crevices and cracks of any buds where a fungus is suspected. Look at the core to see if there are any signs of rot. If the core has a soggy brown appearance, remove the plant, place it into a bag, and separate it from your other plants to prevent contamination.

Examine other plants to see if there are similar symptoms, then quarantine them as well. Be on the lookout for the development of a dusty gray webbing with white spores. Spores travel easily outdoors due to pollinators, water and wind. Even in indoor grow rooms, spores are extremely difficult to control.

If you notice signs or symptoms of bud rot, be sure to change your clothing before proceeding to a different grow room or area. Wearing a protective suit is recommended. There is usually a rotting mildew smell with a foul odor when cannabis bud rot is present. There are three distinct stages to be aware of. During these stages, the mold will mature, then begin releasing spores.

Despite rot initially appearing within the buds during the first phase, there are two specific symptoms to look for once the rot has infected your crop. The first is the appearance of a fluffy white fungus on specific areas of your buds. Look for white spots on the leaves. This is an extremely fragile material. You need to be incredibly careful when handling because releasing the spores will spread the infestation.

Cannabis Bud Rot
An example of a progressive case of bud rot.

The second symptom appears on the bud leaves. These are the smaller leaves growing out of or in between the buds. The leaves often become deformed or have an abnormal pattern of growth. If this symptom appears, check the inner areas of the buds immediately for bud rot. The bud leaves turn brown, with white fluff appearing in spots on certain areas of the buds.

If the mold is discovered quickly, most of your buds can generally be saved by correcting the environment and applying Trifecta Crop Control. This may be a little more challenging for outdoor crops, but we will get to that.

Be sure to cut off and remove all severely infected areas from the plants. If the infection has progressed to this stage, it means a larger portion of your plants are affected.

The signs of bud rot will be much more visible now. Look for greyish brown calyces. The leaves on your buds will become darker, turn purple and dry out. Mushy greyish-brown spots will be visible on your buds. This is where rot is escaping from the cannabis buds. The first spores are small black spots, easily releasing from the plants into the air and this is what will infect other plants in the general area.

During this 2nd phase, immediate action is necessary to save your plants! All infected buds must be removed as soon as they are detected. If your plants are in a grow room, the environment must be corrected and sterilized, or your entire crop can be lost. During this phase, rot is now visible from the outside of the buds, so it is easy to see.

By the third phase, if gone unnoticed and/or untreated, bud rot will infect the entire crop within a few days. Look for mold spores on the plants and buds. By this phase, the process is no longer reversible. The plants will have a fragile appearance, with a covering of gray mush. Within a couple of days, all that will remain are rotten brown buds. Your buds will break down as soon as they are touched.

The insides of your buds are filled with dust containing dark speckles. If they are opened, dust will float through the air and spread. Do not breathe in the small particles dust or you risk becoming ill. This dust is the fungus spores of the rot. If the infestation has advanced to this point, your entire crop is lost. The only remaining option is to accept the loss.

The cause of bud rot must be identified prior to planting again or there is a good chance your new plants or seedlings will be affected as well. All grow rooms must be cleaned thoroughly and sterilized prior to trying to grow anything new because the fungus spores will remain after you have removed the infected plants.

What Causes Bud Rot?

Cannabis strains with a weaker immune system are at a greater risk. The most common causes of this fungus include:

  • High humidity levels
  • Grow rooms with inadequate HVAC
  • Mild temperatures
  • Dense plants
  • Plants with larger buds

What causes bud rot is simple. In most instances, moisture has been trapped by dense plants and large buds resulting in excess wetness. Cannabis bud rot is more of an issue for outdoor growers because it can be impossible to control the environment. If the humidity, ventilation, lighting and temperature are not properly controlled for indoor grow rooms, this can also result in bud rot.

Obviously, it is not possible to control morning dew or rain levels for outdoor crops. This means plants can become saturated day and night. Outdoor growers, especially in coastal areas, need to understand the best way to prevent bud rot. This is a major issue due to the difficulty of controlling the levels of humidity. Dense plants and larger buds are frequently affected because there is not enough air circulation around the plants.

How Fast Does Bud Rot Spread?

Cannabis bud rot spreads extremely quickly and is highly contagious. Both indoor and outdoor crops can become totally infected within just a few days. For this reason, you need to apply preventative measures and treat your plants effectively upon the first sign of infection as quickly as possible to prevent mold from spreading to your other plants. We ALWAYS recommend using Trifecta Crop Control as part of your IPM to ensure pests, mold and mildew never become an issue in the first place.

How to Stop Bud Rot

How to Stop Bud Rot Indoors

There is more than one answer as to how to stop bud rot indoors. First and foremost, you should start by applying Trifecta Crop Control at a dilution ratio of 2oz per gallon, every 72 hours until the infestation is under control. Then switch to a 1oz per gallon preventative at once per week. Our unique formula penetrates mold and mildew on the cellular level and knocks it out quick!

Since excess moisture can result in mold, your plants should be kept on a strict watering schedule to eliminate excess moisture. Mold can result if the temperature in your grow room is too cool because the conditions become ideal for mold germination. The humidity levels in your grow room must be kept low.

Cannabis Bud Rot
Bud rot causing deformation and darkening of leaves.

The ideal temperature for cannabis plants in a grow room is between 65- and 85-degrees Fahrenheit. Temperature is the most critical when plants enter the flowering stage. Mold can also result if the temperature is too warm since mold thrives in moist, warm temperatures. If the humidity is high, the risk of mold increases for every degree the temperature is above the recommended setting.

During flower, the temperature should be closer to 75-77 degrees Fahrenheit. Plants should never be placed too closely together due to the interference with air circulation. This results in the accumulation of moisture, which can lead to mold issues. If there are any symptoms of rot, all infected plants should be removed from your grow room immediately.

Every area with mold must be removed to give your plant any chance of recovery. All removed plants should be kept in a different area to prevent the spread of contamination. Growers recommend a dry, cool area with a good breeze. Do not allow any infected plants to connect with your healthy plants! The best solutions for stopping bud rot indoors include eliminating the following issues:

  • Apply Trifecta Crop Control
  • Overwatering leading to excess moisture
  • Temperature is too cool
  • High humidity levels
  • Temperature is too warm
  • Plants are placed too closely together

How to Stop Bud Rot Outdoors

Same answer as indoors. Trifecta Crop Control should be your go to for mold and mildew. Thanks to nanotechnology, our formula attacks them on the cellular level. Apply Trifecta Crop Control at a dilution ratio of 2oz per gallon, every 72 hours until the infestation is under control. Then switch to a 1oz per gallon preventative at once per week. Weather can affect application. Please contact us if you have any questions. Also, you can click here to view and/or download our complete application guidelines.

Rainy weather can be a driving factor behind bud rot. If possible, construct a temporary shelter for outdoor plants using metal poles and waterproof tarps. This is especially important for rains lasting for more than a couple of days. Another solution for stopping bud rot outdoors is to make sure plants are placed far enough apart when planting. Air needs to have enough room to circulate to ensure overall health.

Excess water provides the ideal habitat for bud rot to form inside of the buds. The areas on the plants with cannabis bud rot should be removed, then disposed of in a sealed bag away from the other plants. As soon as any symptoms appear on the plant, grey mold will follow rather quickly. The mold will spread throughout the plant, including all the buds, before infecting the other plants.

If there is no improvement in excess moisture, humidity or airflow, one small, infected area can destroy your entire harvest. The best option for stopping bud rot outdoors is to remove every plant showing any signs of rot. Place the plants in a dry, cool area with a decent breeze. Make certain the rot does not come in contact the rest of your crop or the infection will spread.

Do not return these plants to the original area. Keep them separate to ensure any mold potentially remaining is confined. The best way to get rid of the rot is to:

  • Apply Trifecta Crop Control
  • Construct a temporary shelter
  • Make certain plants are placed far enough apart
  • Remove any infected areas
  • Move the plants to a dry, cool area with a decent breeze

How to Prevent Bud Rot

How to Prevent Bud Rot Indoors

There are several different techniques for how to prevent bud rot indoors. The first is an application of Trifecta Crop Control with a dilution of 1oz for each gallon. Treat your crops once per week.

In controlled spaces, humidity levels or RH are controlled through having proper A/C tonnage and dehumidifiers. Having the appropriate levels of each maintains proper RH in grow rooms. Additionally, creating a vortex air flow and utilizing HEPA filter air scrubbers reduces the opportunity for mold or mildew spores to colonize.

If humidity levels remain high, defoliating or plucking the undercarriage of the bushiest plants allows for easier air movement, decreasing the likelihood for an outbreak of mold or mildew. You can supplement air flow by adding fans. Thoroughly inspect your plants daily. This will help you discover bud rot faster and potentially eliminate the issue completely.

The densest, longest and thickest buds should be watched extremely closely for any signs of rot. All the solutions below are good options for how to prevent bud rot indoors.

  • Apply Trifecta Crop Control
  • Use an exhaust fan for air circulation
  • Shake plants to remove excess moisture
  • Ensure the humidity remains under control
  • Remove the lower and middle leaves
  • Thoroughly inspect plants every day

How to Prevent Bud Rot Outdoors

An application of Trifecta Crop Control Super Concentrate using the same method described above is a viable solution for how to prevent bud root outdoors. Be sure to blow dew from plants using a leaf blower every morning and after there has been heavy rain. Drying off the plants will prevent them from sitting in wet conditions for long periods of time.

The densest plants with the longest and thickest buds should be inspected daily. The spacing between your plants is critical for preventing rot. No parts of the plants should be touching, and airflow must be able to freely reach all areas around the plants. Proper trellising reduces flower on flower contact. All unnecessary plant material and standing water should be removed to prevent and stop the spread of bud rot.

How to prevent bud rot outdoors can be answered with all the techniques listed below:

  • Apply Trifecta Crop Control
  • Remove excess water using a leaf blower
  • Trellising
  • Thoroughly inspect plants every day
  • Space the plants correctly
  • Unnecessary plant material and standing water should be removed

What to Do if You Get Bud Rot After Harvest?

One of the scariest questions any grower asks is what to do if you get bud rot after harvest. Once a bud has started showing signs of bud rot, smoking or consumption is no longer safe. All infected buds must be discarded. If the cause of the rot is eliminated, and the infection is caught in the earlier stages, there is a chance you can save your crops.

Mold can also develop while your buds are being dried and cured. There are methods growers use to help prevent bud rot. Wait until after a dry spell before harvesting your plants. Outdoor plants should not be harvested if there has been any rain during the last three days. This will ensure the moisture content of your buds is lower.

Allow enough room for the hanging branches during the drying process. Areas between the branches and buds require good ventilation to dry properly. If the plants are dried too closely together, the resulting moisture can cause the rot to spread. Fans placed throughout the room will improve circulation and airflow. Moisture can be effectively pulled from the air with dehumidifiers.

Your drying environment must be optimal to help prevent the spread of bud rot. The optimal environment is dark, has a temperature of approximately 60 degrees Fahrenheit and a maximum of 60 percent humidity for a total of 30 days. Drying speed can be adjusted when necessary. Under normal circumstances, drying should not be rushed. This is because the conversion of THCA is not complete and the chlorophyll has not finished breaking down.

Drying slowly is usually associated with a smoother and more flavorful smoke. If there is any mold involved, the drying process needs to be sped up. This can be accomplished by decreasing the humidity level and increasing the temperature. These steps can save your crop from the growth of mold. The best solutions for what to do if you get bud rot after harvest include:

  • Remove and discard all infected buds
  • Look for rot within the buds after harvest
  • Trim the buds and pull the fan leaves off before drying
  • Make certain there is enough room between the plants when drying
  • Improve airflow with fans
  • Eliminate moisture with humidifiers
  • Ensure the drying environment is optimal
  • Adjust the drying speed
  • Speed up the drying process

How Long Does It Take for a Plant to Recover from Bud Rot?

The answer to how long does it take for a plant to recover from bud rot is dependent on the steps taken by the grower. All rotted portions of the plant including the buds must be removed. The plants then need to be placed in a dry, cool area with a good breeze. Any issues with the environment must be corrected. Bud rot must be kept from encountering any other plants.

The mold must be detected and contained as quickly as possible before the stages progress. Provided all these steps have been followed, it is possible for your cannabis plants to recover within about one week.

Should You Harvest if You Have Bud Rot?

If you are wondering should you harvest if you have bud rot, there is a good chance your plants require dry air and less dampness. It is possible for the growth of your plants to continue once the environment has been improved and the infected buds removed. If the issue with the environment is not corrected, bud rot generally comes back almost immediately.

In order to fix the environment, there are specific steps you must take. Start by improving air circulation. During the late flowering stage, the ideal humidity level is between 45 and 65 percent RH. Leafy plants should be defoliated, with the leaves covering the buds, the leaves not receiving enough light, and the leaves in the middle of your plants removed.

Wet areas on your plants need to be prevented. If your plants are being grown outdoors, no improvements can be made regarding the environment, and the bud rot is in the later stages, consider cutting your losses. If the mold has been removed, but the expected weather is wet or cool, harvest immediately whenever possible. This will prevent mold from spreading to your other plants.

Harvesting early is preferable to the loss of your entire crop. Take extra care when drying the buds. If mold has been an issue, you can dry your crops quicker using a combination of movement and a lot of air circulation. We always recommend using Trifecta Crop Control as a preventative to ensure you do not experience bud rot to start!

What Happens if You Smoke Bud Rot?

Smoking buds containing mold is not recommended. Although some individuals only experienced allergic reactions, others have been poisoned due to toxins the mold produces. Mold is often indicated by a mildew odor. Just the smell alone can result in sneezing and coughing. Smoking moldy cannabis can also result in severe conditions. Consistent exposure to any type of mold can cause several different issues.

This includes increased sensitivity to a range of microorganisms, immunologic lung disorders and infections. The risk of developing these issues increases because of the microorganisms found on cannabis. This issue was studied, with a publication of the report in 2011. The researchers documented two cases of chronic pulmonary aspergillosis resulting from smoking moldy cannabis.

Despite the rarity of this condition, the study showed it can be caused by smoking moldy cannabis. If the individual is suffering from cancer or has a compromised immune system, the diseases resulting from mold can be deadly. Under no circumstances should moldy cannabis be smoked. What happens if you smoke bud rot are potential consequences too severe to take the risk. Once the cannabis has been compromised, the only good option is throwing it away.


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