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botrytis
Botrytis, commonly known as bud rot, is one of the most feared and destructive fungal diseases for cannabis growers. This mold attacks buds from the inside out, often remaining hidden until it has caused irreparable damage. Unlike other pathogens, once it takes hold in a bud, there is no saving that part of the plant, making prevention and early detection paramount.
Removal Options
- Manual removal
- Organic sprays
- Environmental control
- Multi-application
Prevention: Your First Line of Defense
Quarantine:
Isolate any new plants, clones, or cuttings for at least one to two weeks. During this time, inspect them daily with a magnifying glass.
Sanitation:
Keep your grow area clean and free of dead plant matter. Sterilize all surfaces to kill all dormant spores that could end up back in the garden.
Air Filtration & Vents:
Use HEPA filters on all intake vents to prevent spores from entering into your grow room from outside.
Environmental Control:
The single most important factor is maintaining low humidity, especially during the flowering stage. Keep the relative humidity (RH) below 50% during the day and even lower at night (40-45%).
Proper Plant Spacing:
Do not overcrowd your plants. Adequate spacing allows for air movement and prevents moisture from being trapped in the canopy.
Air Circulation:
Ensure there is a constant, gentle breeze flowing throughout the plant canopy and below. Use oscillating fans to prevent stagnant air pockets, which are breeding grounds for mold.
Avoid Wetting Buds:
Do not apply foliar sprays or water plants late in the day during flowering. Wet buds are highly susceptible to botrytis.
Pruning:
Prune away dead or dying leaves and thin the canopy during the vegetative and early flowering stages to improve air flow and light penetration.
Integrated Pest Management (IPM):
Integrated Pest Management (IPM) is a comprehensive, common-sense approach to pest control that focuses on long-term prevention and sustainable solutions. It is not a single method but rather a strategy that uses a combination of tactics to manage pest populations while minimizing risks to people, the environment, and the crop.
The key aspects of IPM include:
- Prevention: The first line of defense, which involves proactive measures to keep pests out. This includes sanitation, quarantining new plants, maintaining a clean growing area, and optimizing the environment (e.g., controlling temperature and humidity) to make it less hospitable for pests.
- Monitoring and Identification: Regular and thorough inspections of plants to detect pests and their damage early. This step is crucial for accurate identification, as knowing the specific pest allows for a targeted and effective control plan.
- Action Thresholds: Determining when a pest population is large enough to warrant action. IPM avoids routine, preventative spraying and instead intervenes only when pests reach a level that could cause unacceptable damage.
- Treatment Options: Applying a hierarchical approach to control. IPM prioritizes the least harmful methods first, progressing to stronger ones only when necessary.
- Cultural Controls: Changing growing practices, such as pruning or adjusting irrigation.
- Manual & Mechanical Controls: Physically removing pests or using traps.
- Biological Controls: Introducing beneficial predators or parasites to control the pest population.
- Chemical Controls: Applying targeted pesticides as a last resort, using the safest and most effective options available.
Treatment & Eradication: How to Get Rid of Them
Once botrytis has infected a bud, it cannot be cured. The only effective "treatment" is immediate and thorough removal to prevent it from spreading.
Manual Removal:
Carefully remove all affected buds and plant material. Cut well into the healthy tissue surrounding the rot to ensure all infected areas are gone. Use sterile scissors or shears and clean them with isopropyl alcohol between cuts. Place the removed material in a sealed bag and dispose of it immediately.
Preventative Sprays:
There are some organic preventative fungicides, often containing ingredients like potassium bicarbonate or beneficial microbes (Bacillus subtilis), that can be applied to healthy plants to protect them from future infections. However, these are preventative and will not cure an existing case of bud rot.
Adjust Environment:
After removing the affected parts, immediately reduce the humidity and increase the air circulation in your grow area to prevent further infection.
botrytis Life Cycle
The life cycle of botrytis, also known as gray mold, is an opportunistic process driven by airborne spores that infect plants under specific environmental conditions.
Spore Germination
The life cycle begins when airborne spores of the Botrytis cinerea fungus land on a plant's surface. These spores are ubiquitous in the environment. Unlike some other fungi, they do not require free-standing water to germinate on the leaf, but they thrive in high humidity (above 50%) and poor air circulation.
Infection and Growth
Once a spore germinates, it sends out a germ tube that can penetrate the plant's tissue, often through a wound or a dying plant part like a spent flower. The fungus then begins to grow from the inside out, feeding on the plant's cells. This internal growth is what makes botrytis so devastating, as the damage is hidden until it's too late.
Sporulation
As the fungus grows, it kills the plant tissue, causing it to become soft and discolored. The rotting tissue is a sign that the fungus is ready to produce more spores. The classic fluffy, gray-to-brown mold seen on the outside of a bud is a cluster of fruiting bodies (conidiophores) that release thousands of new spores into the air, allowing the infection to spread to other plants.
Dormancy and Spread
The new spores can be carried by wind or air currents to infect other plants or remain dormant in the environment on dead plant material. The cycle repeats as long as favorable conditions persist, allowing a single infection to quickly contaminate an entire grow space.
What You Might Be Forgetting
The Stealth Factor:
Botrytis is a "stealth" killer. You can't just look at the outside of a bud. You must regularly inspect the core of dense colas by gently pulling them apart.
Rapid Spread:
The spores can spread to other plants very quickly. A single infected bud can contaminate an entire grow room, making immediate removal essential.
Symptom vs. Cause:
The rotting bud is a symptom; the high humidity and poor air circulation are the cause. Without addressing the environmental factors, the problem will return.
Zero Tolerance:
There is no saving a bud with botrytis. Do not try to trim it off and use the rest of the bud. The fungus and its spores are likely present throughout the entire bud and can pose a health risk if consumed.
The "Cannabis" Factor:
Be extremely cautious with any spray or pesticide on a plant intended for human consumption, especially in the flowering stage. Pesticides can be absorbed and can ruin the final product. Stick to biological controls and natural oils during this phase.