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How To Identify And Prevent Bud Rot On Marijuana Plants


bud rot marijuana

Bud rot is the worst nightmare for marijuana growers. It’s hard to prevent or identify and it will ruin your whole cannabis crop. Bud rot develops on the inside of the buds and spreads very quick. Even when your marijuana is drying, this mold will stay active so make sure you’re well prepared this nasty fungus.

1. Prevention is better than cure

Bud rot, also known as botrytis cinerea or grey mold, thrives best when air is very humid and temperatures are low. It develops in the last phase of the flowering period, when air humidity should be between 30% and 40%. The problem is that humidity will increase as you water your marijuana plants. This is why you have to make sure not to give plants too much water and prevent excess spilling. If you water your plants from underneath, make sure you dose the amount so that it takes no longer than one hour for the plants to absorb all of the water. Also, water your plants when the lights have just turned on. Temperatures are then higher and water will damp or be absorbed quicker than when lights are out and your marijuana plants are ‘sleeping’.  In addition, make sure the space is very well ventilated and excess air is extracted. Fans must blow air between the buds and lamps, preferably an oscillating fan.

When growing marijuana outdoors, place your plants in sunlight and in an area where wind creates enough ventilation. Morning dew can then damp quickly evaporate or you can help get rid of dew by gently shaking it off. The best case would be to place your marijuana plants indoors at night so that cold air and damp won’t harm them too much. By placing plants slightly higher than the ground for better ground temperatures, you help your plant’s resilience against diseases. You can also treat your marijuana plant with Teldor from Bayer. But only use this on the stem during flowering phase so the wax coating does not rinse off easily.

2. Recognizing marijuana bud rot

Keep an extra close eye on your marijuana plants during the last weeks of the flowering period. Always look for diseases and abnormalities, but especially for bud rot. You’ve come too far to see a good cannabis crop go to waste after all the hours you’ve spent cultivating your plants. You can recognize bud rot by inspecting the small one finger leaves growing from the buds. If these are green, you’re in the clear. If these have a yellow or brown color, chances are you have bud rot. These leaves let go easily when removed and do not look healthy. If you see this kind of leaf, remove it immediately and bend open the top carefully and look inside and see if things are looking OK.

3. Intervention

Once you’ve identified bud rot on your plants, you need to act quickly. It might be hard on you, but you have to remove any and all infested buds. Bud rot spreads very quickly and it will ruin your entire crop. Use disinfected scissors to cut out rotting buds. Also be very careful not to touch healthy buds with your infected hands. Check every day for bud rot and cut out infected buds immediately!

Want to know more about growing marijuana? Get a free guide about growing marijuana at this link here. Order some high quality marijuana seeds at this link here.



About Author

Robert Bergman is a master marijuana grower. Robert Bergman is the author of 'Marijuana Plant Care' and 'The Marijuana Grow Bible'.


  1. I have noticed brown unhealthy looking calyxes appear everynow and then.If believe these are a sign to give plant special attention.

  2. We get wicked bad botrytis in Hawaii. People here like to grow under cheap walmart clear sheet plastic over pvc greenhouse covers. They do this without providing proper ventilation, and it just turns into a nasty mess during bud time. Get your plants in the most open area you have, and when it comes harvest time, dry them in a good spot. I have a woodstove in my cabin that helps keep my place nice, dry and cozy.

  3. toGreat write up.
    De humidifiers are a must
    I took out 5 gallons of water
    From a 5×5 tent in 1 day
    Its hard to mimic nature indoirs
    Neem oil is also effective as a prevention to molds
    I would not even take cuttings or flower anything that shows signs of pm or stress
    Crop loss is painfull and expensive

  4. There should be some kind of warning before you display a picture that is so sad. Was this plant saved or was there… just no hope?

  5. Thanks Robert for your helpful information, Botrytis is not always visible on the outside of the plant on the leaves and the exterior of the buds. It will be hidden deep inside the buds right next to the stem. When you find it place a plastic garbage bag over the infected bud in question and make sure it is closed tight and cut the stem below the rotting bud. Remove it from your greenhouse or grow site to avoid spreading the spores throughout your grow. Discard the infected bud with the bag closed. If you choose to try and savage the good parts of the bud if there are any be careful and clean your hands,clothes and trimming tools. Poor air flow will cause this quickly. I have had to throw away a pound a day near harvest. 2010 was a bad year for botrytis in humboldt.

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