humidity is prevalent, a brown, slimy substance can
appear; this is actually the decimated plant tissue.
TREATMENT
Botrytis-infected sections of a plant should be re-
moved immediately in order to prevent it from
spreading to other areas of the garden. If possible,
bag the affected section of plant before cutting it.
This should be done to limit the spreading of spores
as the infected area is disturbed. After the infected
sections of plant tissue have been removed, the rest
of the garden should be treated with a biological
fungicide. To prevent future outbreaks, it is a good
idea for indoor and greenhouse growers to disas-
semble the grow room after the garden cycle and
disinfect everything with a 5-10% bleach solution
or a food-grade hydrogen peroxide solution. This
will kill any remaining viable spores and reduce the
chance of a future outbreak.
PREVENTION
Keeping a clean grow room and removing any dying
or dead plant material are good fi rst steps for any
indoor or greenhouse grower. In a sense, botrytis
is an environmental disease. This means it can only
develop when the environmental conditions are
conducive to its growth. The prevention of botrytis
is somewhat easier for indoor horticulturists because
they have more control over the environmental con-
ditions. Humidity is the biggest trigger for botrytis
in an indoor garden. As long as the humidity is kept
below 55%, botrytis is unlikely to develop.
The other contributing environmental factor is tem-
perature. Botrytis can only germinate on damp or
wet plant tissue in temperatures between 50-70 de-
grees F. However, once the fungus has developed,
it can withstand a wider range of temperature and
humidity. Botrytis grows most rapidly in lower tem-
peratures paired with high humidity. The humidity
levels in close proximity to the plants are generally
much higher due to the plant’s transpiration pro-
cesses. This is why air movement within the grow
space is so important for maintaining proper humid-
ity levels. To create good airfl ow, oscillating fans
should be used to mix the humid air that is close to
the plants, with the air in the rest of the room; this
will help keep the room’s humidity uniform.
OPTIMAL HUMIDITY RANGE FOR INDOOR
GARDENS AND GREENHOUSES
As previously mentioned, maintaining proper
humidity levels in an indoor garden or greenhouse
(Continued on page 26)
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July 2019