Identifying bud rot and salvaging your grow

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Cannabis cultivators are often faced with numerous challenges that sometimes result in the loss of an otherwise would be bountiful harvest. One of these challenges is bud rot, also known as botrytis cinerea. Bod rot is a type of mold that is capable of destroying plants at an alarming rate, leaving growers with steep losses. This is especially true for beginner growers who may not know how to spot the early signs, or how to prevent it from spreading. Learning everything there is to know about this mold and how to salvage bod rot when it occurs puts you in a position to nip the infestation in the bud (no pun intended).

What is bud rot?

Also known as gray mold, bud rot is a type of mold that attacks the stem that the buds are attached to. With time, this interferes with the water and nutrient supply to the buds and leaves, eventually leading to their death. Bud rot is caused by a parasite known as Botrytis Cinerea, and it affects both outdoor and indoor-grown cannabis plants.

Bud rot spreads at an incredibly fast pace which makes it very difficult to stop once it occurs. However, if caught early on it is possible to salvage your crop. We will cover this in more detail further on.

How fast does bud rot spread?

Very fast! The parasite is highly contagious and can quickly destroy your plants within a just few days. To salvage bud rot and prevent it from completely ruining your grow you need to be able to identify the very early signs of bud rot the moment that it begins to take hold. To do this you need to keep a close eye on your plants and continuously assess the appearance of your buds. This is much easier done when you have a small grow of just one or two plants. Once you get into the realms of ten plus plants it becomes a much bigger task to keep on top of.

Of all of the plant infections, botrytis cinerea is one of the most successful pathogens due to its ability to spread using various methods, its high reproductive output, wide range of hosts and its ability to survive. Its main means of spreading is through its airborne spores, this makes it almost impossible to stop once it takes hold.

Stages where your plants may be susceptible to bud rot 

Bud rot becomes a threat from the beginning of the flowering stage until the drying and curing process. That’s right! Even after having a long, successful growth period, your buds are still at risk from Botrytis Cinerea. How fast you trim the buds after harvesting, the drying room conditions, and the curing procedures may or may not lead to bud rot infestation. 

bud rot on marijuana

What does bud rot look like?

Bud rot goes through 3 stages once it strikes. Initially, it presents as a feathery white mold. This is the first sign of the mold working itself from the core of the bud to the outside. If it goes undetected, the mold turns grey and is accompanied by yellow and brown, wilted leaves that appear burnt. The final stage is when the rot turns black. At this point, it is impossible to salvage anything as the damage is already done. The buds become slimy and have a pulpy consistency.

This image (left) is bud rot in its early to mid stages, it has already began to turn a brownish colour. Salvaging bud rot ridden plants isn’t easy, however as this particular patch was an isolated issue and caught early the plant was saved by removing the infected area.

Below is a list of signs indicating bud rot;

  • Yellow, wilted leaves that look burnt.
  • Rotting, foul odor
  • White mold on the flowers/buds
  • Black spots on the leaves
  • Inconsistent leaf growth
  • Rotten buds

What causes bud rot

The most common causes of bud rot are high humidity and poor air circulation, however, there are lots of other contributing factors that allow bud rot to go unnoticed and spread faster. Having a tightly packs grow space with very little room means that not only is air circulation reduced, but its also a lot more difficult for us growers to manoeuvre between plants and properly monitor the grow. Aside from the conditions, genetics themselves can play a major role. Plants that are high yielding and produce particularly dense flowers are more susceptible to bud rot because they require even better air circulation and humidity regulation, especially when grown indoors.

Here are a list of things that you should consider before you start your cannabis grow. Each of these factors play a role in creating conditions where bud rot is more likely to occur:

  • Poor air circulation
  • High levels of humidity
  • Tightly packed grow space
  • Large dense buds
  • High yielding cannabis plants
  • Unsanitized grow rooms

If you ever experienced bud rot in your grow room, if you were lucky enough to salvage your grow, be sure to fully sanitise the tent or space before your next grow. Botrytis cinerea is a highly contagious, any particles of this mold left behind in the grow tent could trigger bud rot occurring again in your next cannabis grow.

Does bud rot affect potency?

Anything that stresses a plant, including bud rot can have an impact on potency. It depends how early on the infection is caught to the extent of which it damages the quality of the bud.

Catch bud rot early during the later stages of flowering and you may be able to remove the infected parts, harvest the rest of your grow and it may have little to no effect at all on the potency. But lets say you don’t spot it immediately, it damages a fair amount of your plant, but you manage to salvage what you have left and finish the grow. The stress that this will cause to your plant will undoubtedly have a negative affect on the potency. Not only will it affect the potency of your plant, if you miss any of the infected areas while removing the bud rot you could end up smoking some, and smoking moldy weed can be damaging to your health so it isn’t a good idea.

It isn’t just the infection itself that causes stress, remember the cure for bud rot is often cutting a large chunk of your plant away. This could completely stunt its growth, cause it to turn into a hermaphrodite, or in the best case cause the plant to halt trichome production while it recovers. This is what will reduce the potency. There is no way to be able tell how badly it will affect your plant, however, the closer you are to harvest day, the less it will impact potency. If bud rot occurs during the early stages of flowering then it will affect the potency of your bud a lot more.

Identifying bud rot

Early detection of bud rot is critical in saving your cannabis plants. Unfortunately, it is impossible to diagnose the disease before it displays any signs. This is because it affects the core of the bud before destroying other parts of the buds and the leaves. To identify bud rot early on you must conduct regular inspections of your plants to get ahead of the situation when it matters. If you suspect your plants may be infested, examine the cracks and crevices of the buds in question. 

Take a good look at the core and if it looks pulpy and brown or has white powdery growth, remove the plant and any others showing similar signs. Put that area under quarantine in case the remaining plants have been infected but are yet to show any signs. Bud rot spores can be easily transferred from one plant to another by wind, water, insects or simply brushing against your clothing. To avoid this, ensure you and all grow room employees wear different clothing when handling the healthy plant section from the bud rot-ridden one. 

using fans to aid airflow can help to reduce bud rot

“Bud Rot is easier to prevent than cure: Use fans to improve air circulation with indoor grows and reduce the risk of bud rot ever occurring in the first place.”

Can you salvage moldy buds?

Salvaging moldy bud is not as easy as preventing it in the first place. However, if a few plants or a section of your cannabis plants have bud rot, the mold may have spread to other areas within the same grow environment. At this point, you need to choose between harvesting everything immediately or isolating the affected plants and letting the healthy ones complete their growth cycle.

How to harvest early to salvage your crop

If your plants are in the later stages of flowering it may be safer to harvest slightly earlier than planned to prevent the bud rot from spreading any further. If you choose to do this it is still incredibly important to isolate and discard any parts of the infected plants. Bud rot can still spread during the drying and curing phases.

  • Remove any infected plants.
  • Carry out a thorough inspection of all of the plants and buds.
  • Once you have separated all of the infected plants be sure to wet trim your healthy plants before drying. This will give you an opportunity to further inspect the buds as you remove any fan leaves.
  • Dry your buds as spaced out as possible, and if you have space use two rooms. Therefore if the bud in one room is infected you will hopefully still have the other half of your harvest that is disease free.
  • Check your buds regularly during the drying stage and discard of any that you suspect of infection.
  • Thoroughly check your buds before the curing stage. Once you are happy separate the buds into multiple containers, this will again reduce the risk of all of your bud being compromised at once.
  • Carry out burping at least 3 times each day and again inspect your buds. if you spot any infected bud, you will need discard of the entire container. This is why it is best to cure using multiple jars or containers.

Should I cut bud rot off of my plants?

Most growers will say, if you find bud rot the entire plant should be removed from the grow room, and while this is certainly the safest measure, what if you’re only growing one plant? And what if you are right at the end of the flowering phase?

If you are only growing one plant, then it may seem like a hell of a lot of hassle to start again from scratch, especially if you are nearing the end of your grow. Depending on how badly infected the plant is and how long you have until harvest you can try to remove the infected parts if you catch the infection early on. Just remember that bud rot is highly contagious, so while you may think you have removed all of the infected areas, there is no way to know if its spores have already spread to other parts of the plant.

Ideally after you have removed the infected parts you should still try to harvest as soon as possible to reduce the chance of it coming back. Just remember even after harvest bud rot can still wreak havoc on your grow. If you have been lucky enough to salvage a decent portion of your plant that appeared uninfected, bud rot can come back during the drying and curing phases. Read on to find out how you can go about preventing this.

How to cull and remove entire plants infected with bud rot

If you are growing multiple plants and they are not yet ready to be harvested you may need to cull any infected plants and continue with the grow. Salvaging bud rot infected plants like this is only going to be possible if you manage to catch the mold early on before it spreads across your grow. Unfortunately bud rot is so contagious that in many cases, even if you do manage to spot it early and cull the infected plants, the spores may have already spread without you knowing, only for your crop to be completely binned later down the line. Just be prepared for this if it does occur.

If you are fortunate enough to have been able to catch the very early stages of bud rot before it has spread then you can continue with your grow by successfully isolating and culling any infected plants. To do this you must….

  • Very carefully remove any plant that shows signs of bud rot and isolate them. Try your best not to brush the infected plant on any others or you run the risk of the infection spreading.
  • Wear gloves and thoroughly sanitise or discard of any equipment used during this process, such as scissors or trimmers.
  • Remove any other clean and healthy plants from the area and sanitise the area where the infected plants were in the grow room. Thoroughly clean any sides, corners, fans or lights that the plant may have been touching before using the area again.
  • Continue with your grow but be sure to carry out regular inspections for any other infected plants.
  • if you have enough room and equipment for this, it is safest to split your grow space into two rooms or areas so as to limit any further damage. This will help you to salvage at least half of your crop.

How to prevent bud rot from occurring

The best way to prevent bud rot from infecting your plants is by providing optimum conditions that discourage the parasite from thriving. Below are tips on achieving this when cultivating indoors or outdoors. 

During the flowering stage

Growing Indoors

  1. If you have bushy, dense plants, try and defoliate the lower and middle leaves to facilitate optimum airflow.
  2. If there is high humidity where you live try growing a strain that is better suited to this kind of climate. Sativas such as Amnesia Haze, Thai Stick and G13 Haze all grow naturally in hot humid environments and have less dense foliage so will be much less susceptible to but rot.
  3. Invest in good quality extraction fans.
  4. Conduct regular inspections of your plants, especially the denser ones.
  5. Maintain a humidity of about 40% to 50% throughout the flowering stage. 
  6. Keep the plants spaced out.
  7. Use humidifiers to regulate the amount of moisture in the grow room.
  8. Maintain a temperature of 75 to 77 degrees Fahrenheit throughout the day. Lower the temperatures by 5 to 10 degrees during the night to allow the plants to cool down internally. 

Growing outdoors

  1. Avoid flower to flower contact by trellising your cannabis plants.
  2. Get rid of unnecessary plant matter.
  3. Drain stagnant water within the cultivation site.
  4. Blow dew from the plants every morning. If you are cultivating cannabis during the rainy season, you can build a temporary shelter to keep the excess water away. Alternatively, you can use an electric leaf blower every time it rains. 
  5. Inspect the plants daily, especially the dense ones.
  6. Space the plants sufficiently.

During the drying and curing process

Once you have reached the end of the flowering phase it doesn’t mean you are completely in the clear, but rot can still strike during the harvesting, drying and curing stages. Use these tips to reduce the chances of your plants being infected with bud rot after they have been harvested.

  • First, you should never harvest your cannabis plants if it has been raining for two or more consecutive days. Harvesting under dry and cool conditions lowers the bud’s moisture significantly. 
  • After harvesting, don’t let the plants sit around for an extended time. This creates an opportunity for mold to strike. 
  • Do not overstuff your drying room. Space the plants such that they do not touch. 
  • Invest in fans to maintain regular, healthy airflow.
  • Keep the plants in a dark room with temperatures of 60 to 70 degrees Fahrenheit. The humidity levels should be at 50% within the first three days then increase to 60%.
  • Trim your buds entirely before starting on the curing phase, or even bettern wet trim your plants before starting the drying phase.
  • Ensure that the buds do not feel moist when touched before initiating the curing phase. The stems should snap and not bend, indicating proper drying.
  • Once you put the buds in an airtight container, ensure you burp them several times a day for the first two weeks. This allows the moisture trapped inside to get out and lets in fresh air. 

Notes:

Cheung, N., Tian, L., Liu, X. and Li, X. (2020). The Destructive Fungal Pathogen Botrytis cinerea—Insights from Genes Studied with Mutant Analysis. Pathogens, 9(11), p.923. doi:10.3390/pathogens9110923.

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