Botrytis cinerea Research 1

Botrytis cinerea (gray mold) on plant species

Botrytis cinerea is a species of fungus that needs a host to grow. We refer to such an organism as an obligate biotroph. In fact, the fungal species needs plant material to reproduce (sporulation). However, B.cinerea produces hard-shelled spores that survive the extremities of bad weather and climate.

The effect of bud rot

Bud rot has caused significant unease in America's legal cannabis grow community. The mold is prevalent on cannabis plants during the time of their late blooming stage. Because of the nature of cannabis use, the growers are unable to use fungicides, as spraying the portions meant for consumption would be a hazard.

There are various methods of controlling Botrytis cinerea on cannabis, and most rely on lowering the humidity, increasing the air exchange and applying fungicide or organic microbial agent.

As the cannabis industry increases in revenue and share holdings, the raw amount of cannabis buds lost to bud rot is frightening. Measures should be taken early if one is to avoid such a pesky fungal plant disease.

About Botrytis cinerea

The fungus starts it's life-cycle as a spore. The spore may be resting for months before ever getting the chance to germinate. But, when such an opportunity reveals itself, the fungal spore germinates out of it's hard shell exterior. What comes out of the exterior is a sort of fungal taproot, called a hysterium. The hysterium will latch onto the plant host tissue. Once attached, the fungal network system can be established.

Not much longer, the plant is covered with visible gray mold. The mold we see with our eyes is the mycelium of the B.cinerea fungus. In humid, congested climates the mold infection is spread rapidly. Conversely, in dry, arid climates the mold infection is halted.

Control methods

Climate control plays a key role in stopping Botrytis cinerea from destroying crops. The main consideration being humidity. If the relative humidity of the grow room area is lowered enough, the mold can be arrested.

Temperature has a slight effect on mold development, however it is not as suitable as a control method, due to the mold preferring the same temperatures that plants can survive. With high temperatures it is possible to knock out the mold infection, although doing so may cause heat damage to plants.

"Cleaning the area around where plants are grown can help to eliminate any residual spores. Simply take a sterilizing chemical agent, such as bleach and water (use with caution) and scrub the surfaces of all offending mold infested areas."
-Ron Rosenthol

Air circulation of the grow room is a prime aspect of preventing B.cinerea from making moldy buds. Oscillation fans are helpful for spreading out the air distribution in the room. Ventilation systems can be adjusted for higher input/output, which will increase the air exchange in the room, thus dropping humidity.


Sunlight/UV light has a noticeable effect on Botrytis cinerea fungi. Too much irradiation causes the fungi to die, although do be careful of any UV exposure when exploring such methods.

Sulfur burners are used sometimes to eradicate molds and mildews in the grow room. We can not recommend their use due to the toxic nature of sulfur. Furthermore, for producing medical marijuana this option should be avoided.

For example, H202 is hydrogen peroxide. That is basically water, with one extra atom of oxygen. By dipping mold infected buds in H202 (or foliar spray), the buds are sterilized and mold eliminated.

A more positive solution may be in prevention. If prevention methods do not work for stopping bud rot then fungicidal options may be considered (depending on the plant bloom stage). When a plant has already got it's second round of white hairs, it may be too late to spray many fungicides. Although, some of the organic options are suitable for control of B.cinerea. Essential strain selection is the best prevention to Botrytis cinerea mold infections.


Methods to Stop Botrytis on Cannabis (Bud Rot, Gray Mold) | Mold Resistant Strains

Evaluation of Potential Hazards during Harvesting and Processing Cannabis at an Outdoor Organic Farm | HHE