How to deal with/prevent bud rot in cannabis plants

How to deal with/prevent bud rot in cannabis plants
Something you don't want to see on your plants!

Cannabis, much like other plants, is susceptible to a variety of pests, diseases, and fungi, including whiteflies, mildew, and more. But none of them are as threatening as bud rot, a tough fungal infection that targets the precious buds of your plants and destroys them in a matter of days.

Luckily, there is plenty you can do to deal with bud rot if it strikes and prevent your plants from an attack in the future.


Bud rot

Bud rot is an infection that affects cannabis plants. As the name suggests, it is characterized by a harsh mold that builds up and destroys the buds of a flowering plant.

Bud rot can be tricky to spot and only starts producing clear visual cues once it is already well underway attacking your plants. The earliest signs of this infection are usually dry, yellow leaves with no clear cause that usually pop up from one day to another (especially after heavy rain).

Once it develops, the fungus tends to look white and hairy, like the regular fungus that you might find on old leftovers in your fridge. From there, bud rot usually starts to look dark brown, black, or even slightly purple. Eventually, buds can become completely covered in a thick, dark dust, and become soft and almost mushy to the touch.

Other buds may become dry and dark. If you break open an infected bud, you’ll usually find the fungus embedded deep inside the flower itself.


Bud rot is caused by a fungus known as Botrytis cinerea. The fungus usually strikes the inside of the buds first, then slowly starts working its way out. It can also affect other plants like grapes, strawberries, and peonies.

The fungus is usually spread from one plant to another via strong winds and rain which help transport the fungal spores. It then infects a new host via a wound (such as a a little cut caused in the stem from training or wind, as well as damage caused by caterpillars or similar bugs).

Once the fungus finds and successfully infects a new host, it thrives on tight, humid conditions.


Because bud rot affects the individual buds of the cannabis plant, it can potentially destroy a harvest by rendering the buds completely non smokeable. Luckily, there are some simple steps to dealing with the fungus when it strikes:

  • Discard any affected buds: The first step to dealing with bud rot is closely examining your plants to find out which buds the fungus has targeted. Remember to look deep inside the nuggets, as that is where it strikes first. Once you’ve identified the affected areas of the plant, you’ll want to trim them off and discard them completely. Don’t try to salvage any infected buds and be extremely careful not to contaminate other parts of the plant by touching them with an infected bud.
  • Once you’ve removed all your infected buds, you can proceed to harvest your cannabis plant, leaving the fungus with no other buds to spread to. Alternatively, you can move on to the next step.
  • If you don’t want to harvest a treated plant immediately, you can try to manipulate your grow environment so as to minimize the chances of any other fungus spores germinating. To do this, you’ll need to provide your plants with extra air circulation, better ventilation, higher temperatures, and lower humidity levels. You’ll also want to prevent the plants from getting wet. Just remember that this is a risky maneuver and may result in spreading the fungus to the remaining buds on your plant.


Just because fungal spores are spread onto your plants, that doesn’t mean that they will automatically develop bud rot. In fact, by making simple adjustments to the environment you’re growing in, you can easily cut back the fungus’ chances of developing and affecting your plants.

  • Increase air circulation: Proper air circulation is vital for healthy, strong cannabis plants. By continually moving air around your grow space, you help to keep the temperature and humidity levels even throughout the entire space. Also, circulating air helps to dry off any humid areas of your plants after watering, hosing, or rain.
  • Keep temperatures warm: Temperature is a key player in helping fungal spores germinate and spread. To deal with bud rot and most other mold-like diseases, it is recommended to keep the temperatures in your grow space above 20°C (68°F). Cooler temperatures are ideal for the germination of bud rot spores.
  • Keep your plants dry: All fungi need moisture in order to germinate. The same goes for bud rot. Hence, to prevent bud rot and other fungal infections in your plants, make sure to keep a close eye on humidity levels in your grow space. The ideal humidity levels for cannabis range between 30-70% depending on which growth stage the plants are in. To help keep humidity levels in check, make sure you cover your plants during rain and shake them after getting them wet to help remove any excess water and speed up the drying process.
  • Prune your plants: Bud rot likes to target big, thick, and bushy cannabis plants where it can easily go undetected between all the foliage. If you notice your plants are getting overly bushy and thick, consider pruning them, especially if you’re growing outdoors in a wet, humid climate. You may also want to look into cannabis training methods to teach your plants to grow in certain ways so that they don’t become too bushy.
  • Keep an eye on your colas: Bud rot makes a habit of going after the biggest, fattest and dankest colas on your plants. Make sure you pay attention to these parts of your plants as they’re extra susceptible to this infection, and treat them as soon as possible if you find signs of bud rot.


Bud rot can destroy entire harvests if not dealt with quickly and effectively. At the same time, it needs particularly humid, hot, and still conditions to germinate. Hence, as long as you keep a close eye on your plants and provide them with just the right amount of air circulation, heat, and humidity, you should be safe from this killer fungus.