POWDERY MILDEW
A
question that is continually asked by
indoor gardeners goes something
like this: “I am controlling my humidity
down to about 55% and the room temperature is maintained at about 75˚F. I
have good air circulation and yet I still
have a powdery mildew problem. Why?”
To answer this question, it is important to think small, very small. At the
microscopic level small. In general,
individual powdery mildew spores are
not visible to the naked eye. If you see
powdery mildew you are looking at
thousands, or hundreds of thousands
of spores piled up. Plant pathologist Dr.
Ken Horst estimated that if the seven
leaves of rose leaf were covered in
powdery mildew, you would be looking
at approximately 3 million spores. Now
that we’ve got you thinking small, let’s
think about what powdery mildew likes
and needs to grow.
The environmental
conditions that are
most favorable for
disease development
in nature are cool
night temperatures
powdery mildew spores are
“individual
not visible to the naked eye. If you see powdery
mildew you are looking at thousands, or
hundreds of thousands of spores piled up.”
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Maximum Yield USA | June 2016
(about 60˚F) with high humidity
(90-99%) and breezy, warm day
temperatures (about 80˚F) with
humidity of 40-70%. Humidity as it
relates to powdery mildew growth
is a relative term, in that powdery
mildew could still thrive even if the