Description: Powdery mildew and black spot are the “one-two
punch” on roses. Powdery mildew is a problem in all
parts of the U.S.
Powdery mildew usually first appears on new growth,
in periods of warm, dry days followed by cool, damp
nights. The new leaves may become curled or twisted,
and the shoots will look badly deformed. Often, the
upper surface of the leaves appears normal, but there
is extensive fungus growth on the leaf undersurface.
Solution: Do not
plant roses in shaded spots, especially in areas which
tend to dry out slowly in the morning. Begin spraying
with Shield-All IITM
Organic Fungicide or Soap-Shield® Fungicidal Soap
when weather conditions favor infection, and repeat
every 7-10 days for as long as needed to control disease.
During times of steady or repeated rainfall, control
may not be necessary until the dry months of late summer.
(Soap-Shield may cause copper toxicity on some rose
varieties. Copper toxicity appears as purple spots and
is more likely to occur outdoors than in greenhouses.)