Anthracnose on Ash
Gail Ruhl, Department of Botany & Plant Pathology,
Anthracnose is the
common name for a type of leaf spot and canker disease caused
by certain kinds of fungi. Anthracnose diseases, each caused
by a different fungus, affect many trees, but are particularly
prevalent on white oak, ash, maple, walnut and sycamore.
Anthracnose infections occur when periods of
cool wet weather coincide with leaf emergence. The fungus that
causes this disease overwinters in diseased leaf litter and stem
fungus becomes active when temperatures warm up again in the late
winter and early spring, producing fungal spores that are carried
by rain and wind to newly emerging leaves. These spores germinate
and initiate new infections. Additional spores are produced
from these early spring infections, and so the cycle of infection,
sporulation, and infection repeats.
The symptoms will vary depending on the type of tree
and the stage of plant development at the time of infection. On
ash, infected, young ash leaves may wither and turn black while
older ash leaves will exhibit brown, marginal, half-moon shaped
discoloration. Although leaf drop occurs, defoliation does not
usually affect overall tree health since trees have plenty of time
to produce new leaves and make the energy reserves needed to survive
Chemical controls are unnecessary since ash anthracnose
seldom causes significant damage to trees. In addition, fungicides
do not cure infected leaves, and spraying after seeing symptoms
is a waste of time and money.
Please refer to publication BP-143 for additional information
on leaf diseases.
See two of our previous articles:
Leaf-spotting diseases are flourishing with all of