| WALNUT ANTHRACNOSE,
GNOMONIA LEPTOSTYLA (FR.) CES. & DE NOT.
is the most common leaf spot disease of black walnut and occurs wherever black
walnut is grown.
The fungus causes small dark brown to
black circular spots up to 1/2 inch in diameter on the leaves. These spots are
usually bordered with yellow. Wet spring weather is ideal for the development
of the disease, although symptoms may not become visible until June or
By mid-August leaves on
trees infected with walnut anthracnose begin to turn yellow and drop. The
growth rate of mildly to heavily infected trees is reduced. Heavily infected
trees may be completely defoliated. Trees are not killed by the disease unless
they are under stress from other causes. Anthracnose may also affect the
quality of the nuts.
your service forester or county extension agent for recommended control.
Fertilization with nitrogen may help reduce the harmful effects of this