Botrytis Cinerea (Gray Mold)
Also known as botrytis blight, botrytis bunch rot, or bud rot
Botrytis cinerea is a parasitic, necrotrophic fungus that ranks among the most destructive plant pathogens on Earth. It attacks over 200 documented plant species — vegetables, fruit crops, ornamentals, and houseplants alike — and spreads through airborne spores that can travel long distances on nothing more than a draft of air. Left unchecked, an outbreak can move through an entire grow space, greenhouse, or garden bed in a matter of days.
200+
Host species
24–48 hrs
Spread window
15–21°C
Ideal temp
> 65% RH
Ideal humidity
What Makes It So Dangerous
Most plant pathogens specialize on a narrow range of hosts, which limits how far they can spread through a mixed collection or garden. Botrytis cinerea is different — it is a true generalist necrotroph, meaning it kills host tissue first and feeds on the dead cells afterward, and it isn't picky about which plant it kills.
Documented on over 200 plant species across nearly every family, from cannabis and tomatoes to strawberries, grapes, roses, and common houseplants.
Produces enormous numbers of microscopic airborne spores (conidia) per lesion — a single infected flower can release thousands within two days.
Survives harsh conditions as dormant sclerotia (hardened fungal masses) in soil and plant debris for years, waiting for the right conditions to reactivate.
Can infect through microscopic wounds, natural openings, or dying tissue (spent flower petals, damaged leaf edges) without any obvious entry point.
Thrives specifically in the cool, humid conditions many other pathogens can't tolerate — meaning it often takes hold right when growers let their guard down.
How It Spreads
- 1
A spore lands on damp or dying tissue — a spent flower, a bruised leaf edge, a broken stem.
- 2
The fungus germinates within hours in high humidity, sending threadlike hyphae into the plant cell walls.
- 3
Infected tissue turns brown/water-soaked, then develops the characteristic fuzzy gray-brown spore mass.
- 4
That spore mass releases thousands of new conidia, carried by air currents, water splash, hands, and tools to neighboring plants.
- 5
Under cool (15–21°C) and humid (>65% RH) conditions with poor airflow, the cycle repeats every 48–72 hours.
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Frequently Asked Questions
What is Botrytis cinerea?
Botrytis cinerea is a necrotrophic fungus commonly known as gray mold or botrytis blight. It is one of the most economically destructive plant pathogens in the world, capable of infecting more than 200 plant species — from houseplants and vegetables to grapes, strawberries, tomatoes, peppers, and flowering ornamentals.
Why is Botrytis considered so destructive?
Unlike specialist pathogens that attack one or two hosts, Botrytis cinerea is a generalist: it can infect almost any soft plant tissue, survives as dormant sclerotia in soil and debris for years, produces millions of airborne spores per lesion, and can infect a plant without any visible wound. Once conditions turn cool and humid, an entire crop or collection can be lost within days.
How does Botrytis spread so fast?
Spores (conidia) are lightweight and travel on air currents, water splash, tools, hands, and clothing. A single infected flower or leaf can release thousands of spores within 48 hours under humid conditions. Because the fungus can also live saprophytically on dead plant matter before attacking living tissue, unremoved debris acts as a constant spore reservoir.
Which plants are most at risk?
Any plant with soft, moist tissue is vulnerable — flowering plants (buds and petals especially), tomatoes and peppers, strawberries, lettuce, grapes, roses, and most succulent-leaved houseplants. Dense canopies, poor airflow, and high humidity dramatically increase risk regardless of species.
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