Each species of powdery
mildew has a limited host range, and powdery mildew on one species of
plant will generally not spread to other unrelated plants.
All powdery mildews
prefer dry conditions on closely spaced plants with poor air
circulation and low light.
Low levels of fungal
infection may show no symptoms but develop when conditions are
Powdery mildew spores
are spread far and wide by wind currents.
Impact/effects on chrysanthemums
Leaves and stems become unsightly and leaves fail to photosynthesise
to full potential resulting in a reduction in plant vigour and overall
health. Plants may become distorted and premature leaf death may
As with other fungal diseases overcrowding and lack of ventilation
will encourage the disease to spread so adequate room and good
ventilation should be provided.
Fungicides available to the home
gardener for powdery mildew control are based largely on two chemical
ingredients - myclobutanil and penconazole. Sulphur applied as a dust
is another form of control.
There are numerous products available
containing these chemical ingredients.