The weather was wonderful for dogwood blooms this spring. But it
wasn’t so great for
the trees themselves.

“We’ve had a lot of powdery mildew this spring, especially on
dogwoods,” said Jean
Williams-Woodward, a plant pathologist with the University of
Georgia Extension
Service.

Warm, humid days and cold nights, she said, are ideal for
powdery mildew on
dogwoods. The fungus usually appears as a white coating on the
leaf surface.

“On some dogwoods the leaves may turn gray or have darker
blotches on them,”
Williams-Woodward said. “This, too, is powdery mildew, but just
older infections.”

However they look, leaves with powdery mildew aren’t long for
this world.

“Once the leaf is infected,” she said, “the fungus moves across
the leaf surface and
blocks the sunlight. Some leaves may remain on the tree, but
most usually fall.”

Homeowners become alarmed when the leaves start dropping off
their favorite
landscape trees. “But the tree will leaf out again,” Williams-
Woodward said.

Powdery mildew infects almost every landscape tree, she said.
But the fungi are
host-specific. Crape myrtles, for instance, also get the disease
but are infected by a
different fungus.

Most powdery mildew fungi will cause the leaves to drop off. The
fungus that infects
crape myrtles, though, is an exception.

“Powdery mildew is very active in late spring through early
summer,”
Williams-Woodward said. “It peaks in June, then drops off some
through the summer.”

Once a tree is infected, she said, there’s no way to control
it. “It helps to rake and
remove the leaves that drop off,” she said. “That will help
protect new growth or next
year’s growth.”

For large dogwoods, nothing else can be done. “There are
fungicides you can use to
prevent powdery mildew,” she said, “but you will never get
enough coverage on a
large tree.”

For young, small dogwoods, homeowners can prevent powdery mildew
infections with
sprays of Immunex. Daconil will work, too, she said, but will
not control the fungus as
well.