What is bud rot?

What does bud rot look like?

What causes cannabis bud rot and how does it get to your plant?

How to stop bud rot for good

How to prevent bud rot in cannabis plants

Frequently asked questions about bud rot

Get rid of bud rot


Most cannabis growers face the risk of fungus problems, and bud rot on weed is one of them. Although it’s a serious issue that could damage crops and reduce yields, it’s possible to prevent and treat it.

It’s essential to understand the nature of this disease and its causes so you can identify the symptoms early and take remedial action. Learn to treat the infection and apply prevention measures to enjoy a bountiful harvest of quality buds.

Let’s discover more about bud rot on marijuana crops.


What is bud rot?

What is bud rot in weed? Botrytis cinerea is a gray mold that thrives in cannabis buds. Typically affecting flowering plants, the fungus appears on the stem inside the nug and spreads undetected during the initial stages. Luckily it’s possible to identify bud rot under a microscope.

The infestation hinders your plant’s ability to absorb water and nutrients. If left untreated, it can result in crop death.

Cultivators face a higher risk of infection when the growing space has poor circulation and elevated humidity levels. Fungi flourish under these conditions.

Dense plants and large buds are more susceptible as they trap and store moisture. Nearby crops are also in danger as the spores can spread.


What does bud rot look like?

What does bud rot look like on weed?

When the fungus attacks your plant, the first noticeable signs of bud rot are white and wispy mold spots on the foliage.

The symptoms appear on small leaves that grow out of or between the nugs. They look deformed or display abnormal growth patterns. Be cautious as these may be a sign of nitrogen toxicity as well. The foliage turns brown, and you may notice white, fluffy spots on some regions of the buds.

When this change happens, inspect your colas for Botrytis. The signs are more prominent at this stage. Calyces appear grayish-brown, and bud leaves darken and turn purplish before drying out. 

The nugs become mushy and slimy as the rot escapes from them. Botrytis also produces spores that spread to other parts of the shrub and pose a risk to crops in the vicinity.

Removing infected buds and sterilizing the growing area at this second stage is vital to avoid losing all your cannabis plants.

Why are my buds turning brown?

If you don’t notice or treat the problem by the third phase, the infection can spread to your entire crop within a few days. The plants end up looking fragile, covered with gray mush.

The result is rotten brown nugs that break apart when you touch them, releasing fungus spores. At this point of the infestation, there’s no remedy. It’s time to accept your loss and start again.


What does bud rot look like


What causes cannabis bud rot and how does it get to your plant?

High humidity gives rise to bud rot on weed plants as the fungus requires water to breed and produce spores. The crops’ surface gets damp when the level hits 100%. If your growing area has poor ventilation, the risk of infestation increases.

Since marijuana buds are dense, they trap moisture, causing condensation inside the nugs. This condition is perfect for mold to form and thrive, which explains why crops are vulnerable to Botrytis during flowering.

Bud rot also comes from other infected crops in the area via the spores they produce. After relocating the sick plants, it’s critical to clear all debris, which is also a source of infestation. Insects are the main culprits in spreading this disease.


How fast does Botrytis fungus spread?

Bud rot on weed plants can increase within a few days, during which the fungus can thrive undetected. Clear signs appear after two to three weeks, but by then, it may be too late to reverse the situation.

The potential severity of the problem emphasizes the need to know what causes bud rot weed so you can identify the threat early.


How to stop bud rot for good

The best way to stop a Botrytis infestation is to tackle the problem before it reaches its irreversible point. Otherwise, you risk seeing your cultivation efforts go to waste.

As the disease starts inside the nugs before you see symptoms on your marijuana plant, it’s vital to identify bud rot’s early signs. We recommend conducting regular checks to detect any affliction.

Different remedial methods may apply as conditions vary from indoor to outdoor growing spaces.


Treatment of bud rot indoors

Once you detect an infection, remove the affected specimen from the rest of your crop immediately to avoid contamination. Keep the other plants in a dry, cool space with lots of ventilation to reduce moisture buildup.

Discard the parts infected with weed bud rot and clean the area of any debris that might contain spores that can spread.

Rearrange your plants to avoid them being too close to each other. Eliminate excess moisture by adhering to a strict and proper watering schedule.

Check to ensure the growing room temperature is around the 65–85°F range. If it’s too cold or too warm, mold can occur. Adjust it closer to 75–77°F during flowering. Keep the humidity level low as the risk of infestation increases for every degree out of the ideal temp range.


Treatment of bud rot outdoors

As with infected indoor plants, remove outside crops with signs of white cotton on the buds and keep them apart from the rest.

Ensure the space doesn’t have excess moisture so the infestation won’t worsen. Keeping the humidity low also helps prevent new mold from developing. If it’s raining, build a temporary shelter to keep your outdoor garden dry. 


bud rot on weed


How to prevent bud rot in cannabis plants

As rotting weed might go undetected in the early stages until it spreads, prevention is the best course of action. 

Growing the right strain, like those from suitable indoor seeds, is vital. Sativa cultivars generally have a better natural resistance to fungi as they originate from humid parts near the equator. They develop buds with a more open form that allows adequate airflow, making it difficult for mold to propagate.

Indicas, on the other hand, come from damp climates, causing them to have lower protection against fungus, like weed plant bud rot. Their nugs are compact, making them more prone to trapped moisture.

Thanks to breeders who combine different strains to develop hybrids, growers get cultivars with the best of both genetics. Keep in mind that having a natural resistance to mold doesn’t guarantee that fungi won’t infect your plants. Other factors influence the level of risk as well.

Your crops’ health and immune strength play a vital role in protecting them from disease. Weaker ones are more vulnerable to attack, so ensure you boost their robustness by providing:

  • Optimal nutrition.
  • High-quality organic soil with beneficial microbes.
  • Adequate hydration without overwatering.

Another way to prevent bud rot in weeds is to arrange your plants at a distance so they don’t touch. Using a trellis reduces contact between flowers. Ensure that air can circulate freely and cover all the areas around them.

As humidity levels are higher in dense spaces, consider applying training techniques to improve airflow. Pruning your plants helps reduce trapped moisture.

When watering, do it in the morning to give your crops time to absorb the liquid. This schedule also reduces humidity when your garden is dark. 

If you haven’t done it before, learn how to dry weed to reduce the risk of mold and enhance the quality of your nugs. 

It’s possible to have a fungus problem on harvested nugs because they contain liquid. The moisture and darkness of your storage container create an environment for breeding mold. The drying process keeps your cannabis fresh longer, and you’re less likely to have bud rot in dried weed.

Aside from these general preventive measures, additional steps are necessary depending on whether you cultivate in or outdoors.


Indoor bud rot prevention

Ensure the climate in your growing space is consistent when cultivating indoors. Keep humidity levels low by providing adequate ventilation and installing fans and dehumidifiers. If it’s too hot, an aircon unit may be necessary. 


Indoor bud rot prevention


Avoid overwatering your crops as the unabsorbed moisture evaporates and remains in the room, making it more humid. Remove the bottom leaves of bushy plants to improve airflow. A temperature control system enables you to monitor and maintain ideal conditions for optimal growth. 

Inspect your plants daily to detect signs of Botrytis, like black weed bud. Take remedial action immediately if you spot any red flags.


Outdoor bud rot prevention

Once you know what causes bud rot on weed outdoors, implement the following general mold prevention measures:

  • Choose outdoor weed seeds with natural resistance to fungi.
  • Use quality soil.
  • Feed your crops the nutrition they need to grow healthy.
  • Keep your plants apart to facilitate air circulation.
  • Prune dense foliage to reduce humidity.
  • Eliminate moisture buildup by not overwatering and doing it in the morning.


Keeping humidity levels down may be challenging in coastal areas. Veteran growers suggest using an electric leaf blower every morning and after a downpour to blow the dew off your crops. It helps dry off your plants, preventing them from remaining wet for too long.

Knowing how to spot bud rot enables you to treat your weed as soon as you detect the infestation.


Frequently asked questions about bud rot

This section answers growers’ queries and provides additional information on this cannabis fungus problem.


Should you harvest if you have bud rot?

Yes, it’s best to collect your yield early when you detect a Botrytis infection. Even if you remove the affected parts, a recurrence is possible. Salvage your buds before the damage worsens, or you risk losing the whole crop.

Ensure you follow the proper method of curing cannabis, so your nugs don’t become a breeding ground for more mold.

Harvesting weed with bud rot is necessary to prevent the fungus from infecting the rest of your crops, but there are some other things to do. Check the environment and fix trouble spots to foil another attack.


How long does it take for a cannabis plant to recover from bud rot?

The recovery period depends on the remedial actions you take. Remove all the infected parts, making sure you dispose of them without leaving debris containing spores. Relocate the plant to an airy, cool, dry space to avoid humidity problems or another infection.

After taking these measures, your marijuana crop can potentially recover within a week.


Can you smoke rot weed? What would happen?

Yes, you can, but there are risks when smoking weed with bud rot. For most users, moldy weed doesn’t taste good and could cause nausea and vomiting, although these side effects don’t last long.

If you’re allergic to mold or have a weakened immune system, you might end up with inflamed lungs and sinuses. People with respiratory conditions like asthma could experience a severe reaction if they smoke dried bud rot weed.


Get rid of bud rot

Learning what causes bud rot on weed plants gives you a fighting chance against a deadly fungus that can potentially destroy your nugs. Use the knowledge to prepare your growing environment and ensure it doesn’t serve as a breeding ground for Botrytis colonies.

Although the fungus infestation is more prominent during flowering, there’s also a risk after harvest. Put your stash through a proper drying and curing process to minimize the incidence of bud rot on cured weed.

Besides setting up optimal cultivation conditions, remember to grow cannabis strains resistant to fungi to reduce the risk of mold problems. Check out our store to choose from a wide range of premium marijuana seeds.

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