Powdery mildew

Natural History
Powdery mildew on crape myrtle
Photo credit: UF/IFAS

Powdery mildew is caused by several genera of fungi in the Ascomycetes. Powdery mildew can affect a very wide range of hosts an is usually observed most frequently later in the summer following humid weather conditions. The disease is given its name from the presence of the white fungal growth on the leaf surfaces which appears like white powder. There are several methods for controlling powdery mildew including preventative fungicide applications, planting resistant species or cultivars or increasing air movement and eliminating conditions that favor the disease.


 

Identifying Characteristics

Identifying the injury: Distorted leaves, defoliation and sometimes reddening or chlorosis of affected leaves.
Identifying the fungus: White mycelia and chains of spores on leaf surfaces. Sometimes black cleistothecia (sexual fruiting bodies) are seen among the white fungal material. Under the dissecting scope the ornamentation and appendages of cleistothecia can be beautiful and are useful in genus-level identification.
Susceptible trees: Many hosts – commonly on laurel oaks, dogwood, maple, crape myrtle and sugarberry in Florida.

 

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