Blackwelder column: Powdery mildew is a common disease

Published 12:00 am Sunday, June 14, 2020

My neighbors noticed something a little different on their shrubs this past week. There were powdery white splotches on the leaves and stems of their crape myrtles and other plants. Powdery mildew is a very common foliar disease that can be found on many ornamentals and vegetables. The disease initiates as a small powdery blotch but will soon cover the foliage. The fungus often distorts the leaves of dogwood, crape myrtles and perennials. It will outright kill many vegetable plants such as cucumber, squash and other cucurbits.

Powdery mildew is a fungal disease that occurs in early summer during temperature ranges from 60 to 80 degrees coupled with high humidity as experienced over the past few weeks. Shady locations are also a contributing factor to powdery mildew plant infections.

The fungus has become a very common problem, especially in the South. Plant breeders and researchers of both ornamentals and vegetables have developed plant varieties resistant to this ongoing disease problem. It’s important to carefully select newer varieties that have powdery mildew resistance. Try to place susceptible plants a sunny location in the landscape or vegetable garden. Spacing out your vegetable plants encourages good air flow that will reduce the incidence of the disease. If practical, pick off and properly dispose of infected leaves. There are a number of fungicides that will prevent powdery mildew infections; however, most fungicides must be applied before infection to protect the plant.

Darrell Blackwelder is the retired horticulture agent and director with the North Carolina Cooperative Extension Service in Rowan County. Contact him at deblackw@ncsu.edu .

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