Powdery mildew is a common disease on many types of plants and is prevalent under the diverse conditions found in
many areas of California. Different powdery mildew fungi cause disease on different plants. These fungi tend to infect
either plants in the same family or only one species of plant. You can recognize this disease by the white, powdery mycelial
and spore growth that forms on leaf surfaces and shoots
and sometimes on flowers and fruits. Powdery mildews may infect new or old foliage. This disease can be serious on
woody species such as rose, crape myrtle, and sycamore where it attacks new growth including buds, shoots, flowers,
and leaves. New growth may be dwarfed, distorted, and covered with a white, powdery growth. Infected leaves generally
die and drop from the plant earlier than healthy leaves. Wind carries powdery mildew spores to new hosts. Although relative humidity requirements for germination vary, all
powdery mildew species can germinate and infect in the absence of free water. In fact, water on plant surfaces for
extended periods inhibits germination and kills the spores of most powdery mildew fungi. Moderate temperatures of
60° to 80°F and shady conditions generally are the most favorable for powdery mildew development. Powdery
mildew spores and mycelium are sensitive to extreme heat and sunlight, and leaf temperatures above 95°F may kill
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CategoriesFlowersPlant and Tree disease |
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