Recognizing Bud Rot, also known as Botrytis Cinerea or Grey Mould). One way of catching the presence of bud rot in good time is to keep a close eye on the leaf that grows out of the bud. When this takes on a strange colouration (see photos below) and is effortlessly pulled free from the bud with a gentle tug, then you can be 99% certain that there’s rot inside that bud.
The causes of bud rot include dead leaves falling with the arrival of autumn, spiders webs, the larvae and cocoons of insects... they all rot in your plant. The most usual cause and a very common fungal disease in cannabis is pythium. This mould leads to root rot and rotting of the lowest section of the stem. It usually attacks young plants and clones. Bigger, healthier plants are much less susceptible to pythium. In serious infestations of pythium the plant get ‘toppling disease’. We don’t have to spell out what that means.
Pythium can be recognized by the way the bark turns brown at the base of the stem. In the beginning the brown scale can easily be removed, later the rotting process goes even deeper in to the base of the plant.
Pythium is a mould, which thrives best in wet and moist environments. The spores of pythium are only spread via water. There are two types of spore formed: swarm spores and rest spores. The swarm spores germinate best at a temperature of around 15 degrees C., while the rest spores start growing in the warmth, so at about 28 degrees C.
To prevent infestation by pythium a constant soil temperature is desirable. Large temperature fluctuations should be avoided. You also need a good level of humidity (so not too high an RV).
Leaf moulds, mildew and filament fungi are less common than pythium. Mildew can cause bud rot among other symptoms. Other causes of bud rot include the leaves that fall in autumn, spiders’ webs, and the larvae and cocoons of insects.
Prevention is difficult in a western European climate because this mould prefers low temperatures and high air moisture content – something that in this part of the world is pretty unavoidable. Try to keep the plants as dry as possible. It’s an idea for example to shake the morning dew off your plants each day, and to place them in direct sunlight and in a spot where the wind creates sufficient ventilation. The most optimal situation is to bring your plants indoors each night so that they avoid the worst cold and dampness. Placing the plants a little above the ground will also keep the soil temperature a bit more stable and means their resistance falls less dramatically, leaving them more able to fight off diseases.
Another solution for next year is to darken the plants early to that they flower before the autumn raises its damp head. The buds will also be able to make use of the power of the sun during the summer months and will probably be a better quality as a result.
It is also worth preventative spraying with Bayer’s Teldor during the growth period, twice (or 1 x Teldor and 1 x Finesse to avoid resistance), and again once the bloom begins. During flowering, only spray on the stems. Teldor binds with the waxy leaf layer and so does not easily wash off.
The only thing you can do against it during flowering is to trim off the infected branches and sterilise your scissors in between each removal. You’re dealing with a fungus and fungi release spores that can very easily infect other parts of your plant. It’s worth trying to cover the infected leafage with a plastic bag before you cut it off, to reduce the spread of spores.
Work precisely and very hygienically therefore, and continuously check your plants for new infections. As soon as any bud rot occurs in your plant it is usually a lost battle, so in a real emergency the best thing is to just harvest your ladies good and early and by doing so hope to salvage some of the harvest.
In the event that mould affects the stems and branches it can be kept reasonably under control by smearing the affected area with old-fashioned ‘green soap’, a well-known thick paste cleaner bought in a pot, applied with a small brush. The basic (alkaline) environment will stop the mould, the spot will turn black and deterioration will stop. Just don’t rub it into the buds! I’ve used it for years in cases of infection and it makes sure that the branch or stem remains a while longer and that spore release does not take place.
Another option is to remove as much as possible of the affected areas and then scrub lightly with a 3-10% solution of hydrogen peroxide. The stems and trunks can also be smeared with a mix of Teldor, bleach and Dettol (don’t spill on the roots!).
Smoking weed with bud rot or other moulds is not recommended! The best chance you have of salvaging anything is to use water curing (see note on the subject).