POWDERY MILDEW
mildew spores are transported
“Powdery
through the air and land on plant surfaces
and lay in wait for the perfect environmental
conditions for reproduction.”
air humidity is low. For example, an outdoor gardener
who waters the garden in the evening is physically putting
moisture on the leaf surfaces, so even if the air humidity is
low, the necessary ingredient for fungal growth—water—
has been artificially introduced.
Powdery mildew spores are transported through the air
and land on plant surfaces and lay in wait for the perfect
environmental conditions for reproduction. In general,
spore germination occurs at the 60-64˚F range with high
humidity, or leaf surface moisture. At this stage, mycelium (tube-shaped structures), grow out from the spores.
Root-like structures called haustoria burrow into the plant
surface and extract nutrients.
Stalk-like structures called conidia grow out of the
mycelium and new spores stack up like loosely connected
balloons. These new live spores need only a bit of warm
wind and they burst off and float through the air. The
ideal environment for powdery mildew spores to spread
is warm, dry, breezy conditions. So even the most perfect
conditions of low humidity and warm, breezy air spreads
existing mildew spores all over. In fact, what we think
of as perfect conditions are actually necessary to spread
spores, which then land on plant surfaces and wait for just
the right temperature and moisture to start reproducing
again. And herein lies the problem.
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Maximum Yield USA | June 2016