powdery mildew on roses - Knowledgebase Question

wilmington, No
Question by sarahretire
August 13, 2010
In southeast NC will watering at 5:00 cause powdery mildew on rose of Sharron and confederate roses. This year the whole plant is covered, and blowing it around.


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Answer from NGA
August 13, 2010

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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. For heavy infestations of powdery mildew, sulfur or copper sprays can be applied now and reapplied weekly. If you have problems each year with powdery mildew you can start a preventative spray program, starting in June in your area. Products registered for use against powdery mildew 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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