lilac white spots - Knowledgebase Question

o\'fallon, Mi
Question by baconfzn
July 6, 2010
I have a lilac bush that gets morning to mid-day sun. Each year in July is starts getting covered with white spots on the leaves that spread thoroughly. I've cut away old growth, but still get the spots on the new growth as well. Can this be


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Answer from NGA
July 6, 2010

0

Sounds like a disease called Powdery Mildew. Powdery mildew fungi spread quickest when the humidity is high and temperatures are between 50F and 90F. To discourage the disease, plant on sites with good air drainage, give the plants plenty of space, water during the morning only, and allow the soil to dry out between waterings. Remove any affected leaves, as soon as you recognize the white spots to help control the spread. For heavy infestations of powdery mildew, sulfur or copper sprays can be applied weekly, starting in June in your area. These include: sulfur, neem oil (Rose Defense, Shield-All, Triact), triforine (Ortho Funginex), or potassium bicarbonate (Kaligreen, First Step) Chemicals are most effective when combined with cultural controls. Best wishes with your landscape!

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