bud rot botrytis grey mold

Bud Rot (Botrytis) On Cannabis: Prevention And Treatment

Basic knowledge about fungi and mold like bud rot is essential for anyone growing cannabis. Fungi are a real blight, but each species is different, calling for a unique approach. Mildew for instance – another infamous cannabis killer – can be treated using vinegar. That’s not going to work with bud rot, though: infested buds must be removed ASAP. That makes it crucial to detect botrytis early on, followed by immediate, merciless action. This blog tells you how to deal with bud rot in the best possible way.

[Special thanks to Totogrow for his images]

What Is Bud Rot?

Bud rot (botrytis or grey mold) is a fungus that affects many different plant species. In the case of cannabis plants, bud rot prefers to infest the stems inside the colas themselves. That makes botrytis hard to detect in the early stages of infestation. Once it gets a foothold, though, it will spread fast, eating its way through the whole bud and threatening other plants nearby. Bud rot produces airborne spores that can lay waste to entire tents or garden patches in no time.

bud rot botrytis
The culprit from up close. (Courtesy of Totogrow)

Make no mistake: botrytis will destroy affected buds completely. What starts out as some innocent-looking white fluff will quickly turn grey and then black. The cola on your weed plant will start to look sickly as leaves and pistils go pale and wither. In the end, your bud will be a pitiful, slimy, mushy mess. If you don’t act in time, bud rot spores will quickly attack adjacent buds and surrounding plants.

Bud Rot In Your Weed: Know What To Look For

If your grow gets attacked by bud rot, you’ll want to act as soon as possible. That’s why it’s important to know the early signs. The biggest botrytis threat looms in the flowering stage, as that is when the buds develop where the mold prefers to nestle. A major problem with bud rot is its tendency to start at the core of the cola, where it is hard to spot in time. That makes regular checks indispensable: daily inspections are the best prevention. Carefully examine the buds, preferably using latex gloves or tweezers to prevent damaging the trichomes. Be extra vigilant after rain, fog, or other damp conditions.

bud rot prevention
(Courtesy of Totogrow)

Once a bud gets hit by mold, it becomes unfit for consumption. Smoking weed with bud rot is dangerous: you really don’t want fungus in your lungs. If the bud rot hasn’t spread far yet, you can remove infested buds and leave the rest of the plant intact. If you detect multiple moldy buds, it’s probably best to get drastic and remove the whole plant, root and branch. The sooner you act, the better.

Be very careful when cutting away infested buds. Make sure your fingers or cutters don’t spread spores to other parts of your plant, or – worse – to unaffected plants or another grow tent!

bud rot botrytis mold weed
At this point, your bud is far beyond saving… (Courtesy of Totogrow)

The Best Ways To Prevent Bud Rot

Of course, with bud rot, prevention is better than cure – if cutting flowers away can be called cure in the first place. If you want to prevent bothrytis, make sure conditions for fungi are as unattractive as possible. Mold loves moisture and high air humidity. They thrive in dense foliage and compact buds, as well as on plants with weak immune systems. Poor ventilation is another pull factor. These are all factors to keep in check.

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Milkshake Kush Autoflower

Moisture And Ventilation

One of the ways to improve humidity and ventilation conditions is defoliation, or cutting away excess foliage. Dense canopies impede air circulation and increase humidity. Keep your plants pruned to make bud rot conditions less inviting. Supercropping can be a useful technique here, increasing the space between branches and buds.

bud rot cannabis
Detecting bud rot calls for firm cutbacks. (Courtesy of Totogrow)

Try to prevent your plants from being too damp. Water them in the morning to keep air humidity low when darkness falls or the lights go out. Indoor grows have the benefit of not having to deal with rainy weather. On the other hand, ventilation tends to be better outside in the breeze. Outdoors, rainfall can drench buds, making for perfect bud rot conditions. You could take a tour around the garden after  the rain passes and give your branches a few gentle shakes to lose excess moisture. That seems a small price to pay for protecting your harvest.

Indoor growers should always maintain ideal climate conditions by using dehumidifiers and ventilators. A hygrometer is a handy tool to monitor air humidity in tents and grow rooms.

Cannabis Plants’ Immune System

Healthy plants are less susceptible to fungi of all kinds. Treat your weed to the best nutrition for optimal immune system functionality. Soil quality is another important factor in fungal growth. Using minerals, fertilizers and mulch such as wood chips make for a healthy substrate promoting beneficial microbial soil life. Microbes play an important part of your plants’ natural resilience.

Pick The Best Cannabis Strain

Your choice of weed strains is another part of the battle against bud rot. Differences between indica and sativa-dominant strains provide some guidance. Do keep in mind, however, that most modern strains are hybrids containing indica genetics as well as sativa traits. More importantly, know that any strain can succumb to fungi like bud rot. Prevention is always better than cure, so don’t fall for illusions of safety once you’ve found a strain with high fungal resistance!

Sativa-Dominant Strains

Originally, Cannabis sativa strains grew in humid regions near the equator. That heritage tends to make strains with strong sativa components more used to fungi, with better natural resistance. The way the plants develop also helps prevent mold as much as possible, as sativa buds tend to be more open-structured and airy. This promotes air circulation inside the buds.

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Grapefruit Superstar is a super-sativa and know to be resistant against top rot!

Indica-Dominant Strains

By contrast, Cannabis indica is more adapted to the dry mountain air of its central Asian origins. Buds on indica-dominant strains tend to be more compact than their sativa counterparts. Grown in damp climates, they have less natural protection against mold like bud rot. Still, as mentioned, most of today’s strains combine sativa and indica traits in their genetic makeup. That brings out the best of both worlds, with increased fungal resistance as an added benefit.

protecting cannabis from bud rot

Enjoy Bud Rot Free Harvest!

All in all, staying alert for mold such as botrytis is always a good idea. The right amount of care and attention for your cannabis plants can go a long way towards optimal fungus protection. Make sure to buy cannabis seeds with good resistance, such as Lemon Haze or Super Silver Haze, for instance. If you stay sharp and act fast if necessary, you have a pretty good chance of enjoying that glorious mold-free harvest soon!

Disclaimer: Local laws and legislation on cannabis cultivation and germination of seeds vary between countries and states. Amsterdam Genetics products and information are exclusively intended for use in areas where such use is fully legal. Check your local rules; do not act in conflict with the law!

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Super Silver Haze

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