POWDERY MILDEW
Powdery mildew is a fungal disease that can affect a
wide variety of plants. Powdery mildew is a general
term for the plant disease caused by multiple patho-
genic fungi; all found in the order Erysiphales (a
subcategory of the division Ascomycota).
IDENTIFICATION
Plants infected with powdery mildew look as if
they have been sprinkled with white fl our. Powdery
mildew usually starts off as small, circular spots on
the leaves, but can also be found on the stems or
fl owers. In some cases, powdery mildew can cause
the leaves of a plant to twist, break, or become dis-
torted. The white spots eventually spread and cover
the majority of the leaf’s surface.
TREATMENT
Although systemic fungicides are effective against
powdery mildew, they should only be used on or-
namental plants. For food crops or other consum-
ables, the best treatment option for powdery mildew
is some sort of organic-based fungicide. The most
commonly used organic fungicides are sulfur-based
fungicides, copper-based fungicides, neem-based
fungicides, bicarbonate-based fungicides, botanical-
based fungicides, and biological fungicides. Even
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when using an organic fungicide, it is of the utmost
importance to follow the manufacturer’s application
instructions for safety.
PREVENTION
A key to preventing powdery mildew is to make
sure the spores never enter a garden in the fi rst
place. Perhaps the most common way pathogenic
fungi spores enter a garden is through the fresh air
intake. By using an intake air fi lter, a grower can re-
move many of the spores and pest insects that could
otherwise end up in the grow room. A HEPA fi lter
on the ventilation’s intake can be a valuable tool to
lessen the ability of powdery mildew spores to enter
the garden. Fungi spores are microscopic and, even
with intake fi lters, are almost impossible to stop
from entering the grow space.
With this in mind, a grower should focus his or her
attention on humidity control as another preven-
tative measure. Maintaining proper atmospheric
conditions will help prevent the humidity levels
conducive for unwanted visitors. In layman’s terms,
humidity levels are affected by the moisture con-
tent and the temperature in the garden area. This
is why the temperature variance from the lights
on cycle to the lights off cycle is an important fac-
tor to consider. Keeping the temperature variance
www.GardenandGreenhouse.net
July 2019