The Q&A Archives: Variegated privet diseases

Question: I have variegated privet (ligustro abigarrado) in southern mississippi planted around my house for the last 3 years. Last year we lost one to what appears to be a white powdery mold or fungus. It seems to be spreading throughout the flower beds. It can down and killed a second this year and has moved on to a third and 4th planted together. I have used Daconil fungicide on it with no results. The fungus/mold also doesnt affect any other plants in the beds (boxwoods and gardenias). What can I use to kill this.

Thanks in advance
alan duncan

Answer: Powdery mildews, as the name implies, often appear as a superficial white or gray powdery growth of fungus over the surface of leaves, stems, flowers, or fruit of affected plants. These patches may enlarge until they cover the entire leaf on one or both sides. Young foliage and shoots may be particularly susceptible. Leaf curling and twisting may be noted before the fungus is noticed. Severe powdery mildew infection will result in yellowed leaves, dried and brown leaves, and disfigured shoots and flowers. Although it usually is not a fatal disease, powdery mildew may hasten plant defoliation and fall dormancy, and the infected plant may become extremely unsightly.

Most powdery mildew fungi produce airborne spores and infect plants when temperatures are moderate (60 to 80 degrees F) and will not be present during the hottest days of the summer. Unlike most other fungi that infect plants, powdery mildew fungi do not require free water on the plant surface in order to germinate and infect. Some powdery mildew fungi, especially those on rose, apple, and cherry are favored by high humidities. Overcrowding and shading will keep plants cool and promote higher humidity. These conditions are highly conducive to powdery mildew development.

Fungicides can be used to achieve acceptable control. For best results with fungicides, spray programs must begin as soon as mildews are detected. Spray on a regular schedule, more often during cool, damp weather. Use a good spreader-sticker with the fungicides. Be sure and cover both surfaces of all leaves with the spray. Fungicides generally recommended for powdery mildew control include: Triadimefon (Bayleton, Strike); Triforine (Funginex), Thiophanate-methyl (Cleary's 3336, Domain) and Propiconazole (Banner).

Best wishes with your privets!

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