Botrytis (Gray Mold): The Silent Bud Killer — Prevention, Detection, and Emergency Response

AZ_Growshop_Asia · 2026年07月26日10:01

Botrytis (Gray Mold): The Silent Bud Killer — Prevention, Detection, and Emergency Response

Botrytis cinerea destroys more cannabis flower at the finish line than any other pathogen.

Asiannabis Community | Diseases, Insects, and Mites › Botrytis | Updated: July 2026

1. Why Botrytis Is the Number One Threat in Late Flower

Botrytis cinerea is a necrotrophic fungus — it kills plant tissue and feeds on dead cells. It targets dense, mature flower clusters during the final weeks of flowering. Dense bud architecture traps moisture, limits airflow, and provides abundant organic matter. A single infected bud spreads spores to neighbors within days.

Infection Conditions

Factor	Critical Threshold
Relative humidity	>60%, risk increases sharply above 65%
Temperature	15-25°C (optimal ~20°C)
Free water on surfaces	Any condensation
Air circulation	Poor/stagnant
Bud density	Dense, tightly packed
Wounded tissue	Pruning cuts, dead leaves in buds

2. Identification

Early signs (often missed):

Single sugar leaf in bud turns brown while surroundings look healthy
Small section of bud drying prematurely
Localized soft spot when gently squeezing a large bud
Faint musty or sour smell

Confirmed infection:

Gray-brown fuzzy mold on bud surface (spore-producing stage)
Brown, slimy interior when bud is pulled apart
Dried, shriveled buds in advanced cases

3. The 8-Point Botrytis Defense

3.1 Humidity: Keep RH below 55% during final 3 weeks. Monitor at canopy level, not wall.

3.2 Air Circulation: Oscillating fans through and around the canopy. Airflow beneath SCROG screens.

3.3 Temperature: Less than 5°C day/night swing. Nighttime above 18°C.

3.4 Canopy Management: Defoliate strategically weeks 1-3 of flower. Lollipop lower canopy. Don’t overcrowd.

3.5 Leaf Management: Remove dead leaves IMMEDIATELY. Clean floor and surfaces.

3.6 Watering: Water early in light period. No foliar spray during flower. Reduce volume final 2 weeks.

3.7 Strain Selection: Dense Indica buds = more susceptible. In humid climates, prefer loose flower structure.

3.8 Beneficial Microbes: Bacillus subtilis (Serenade), Trichoderma harzianum, Gliocladium roseum. Preventive only.

4. Emergency Response

Turn off fans before touching infected plant (prevents spore spread)
Cut infected bud 5-10cm below visible infection into healthy tissue
Seal in bag immediately, remove from room
Sterilize tools with 70% isopropyl after every cut
Inspect every plant — focus on largest, densest buds
Drop humidity to 45-50%, increase air circulation
Consider slightly early harvest if widespread and buds near maturity

5. Drying and Curing

Parameter	Safe Range
Temperature	18-22°C
Humidity	55-65%
Air movement	Gentle, constant
Duration	7-14 days

Burp jars daily for first 2 weeks. Discard any buds with mold signs. Mycotoxins are NOT eliminated by drying.

6. Can Infected Buds Be Salvaged?

For smoking/vaping/edibles: No. Mycotoxins are not destroyed by heat. Harmful if inhaled.
For extraction: Controversial. GACP/GMP operations reject ALL contaminated material.
Default: Discard all visibly infected material + 10cm surrounding tissue.

7. Tropical Climate Challenges

Southeast Asian growers face elevated risk during rainy season (May-October). Recommendations: indoor with climate control for dense strains, Sativa landraces for outdoor, time flowering to avoid peak monsoon, smaller more frequent harvests (SOG).

Have you lost buds to Botrytis? What environmental adjustment made the biggest difference? Share below.

Part of the Asiannabis Community series on pest and disease management.