Leaves have been falling from sycamore trees. This early loss of leaves can be alarming. A close look at the fallen leaves will reveal brown areas that typically follow along the veins of the leaves. These areas of browning are often V-shaped.
Anthracnose tends to be most severe when extended cool and wet weather occurs in the spring. The fungus that causes sycamore anthracnose needs wetness in order to infect the leaf tissue. Leaves are most vulnerable to this fungus during the first weeks of growth.
Unfortunately, the anthracnose fungus can also cause death of buds and twigs on sycamore trees. The death of new shoot growth for repeated years can result in a gnarled or crooked branch growth as side shoots take over as the new leader branches. The fungus can survive the dormant season on diseased leaves that have fallen to the ground or on diseased twigs that remain on the tree.
Damage caused by the anthracnose fungus is usually minimal so fungicide use is rarely warranted. Chemical control can be problematic because proper timing can be difficult to predict from year to year and adequate coverage of big trees is difficult.
As hot and dry summer conditions arrive, the fungus is suppressed. New shoots emerge and new leaves appear.
This article originally appeared in the June 15, 2001 issue, p. 71.