Control PLANT DISEASES
For Better Farming And Better Living

Mimeo BP 2-1

SYCAMORE ANTHRACNOSE
Almost every spring, Indiana's famed sycamores are attacked by
a fungus disease known as sycamore blight or anthracnoseo The Lon-
don plane tree and certain types of oaks may also be attacked to a
lesser degree by the same disease. Sycamore blight or anthracnose
is primarily a leaf disease, but may infect the twigs and disfigure
the tree. Defoliation and killing of the twigs weakens the trees
but seldom causes their death. This blight is the main reason for
the ragged appearance of sycamores in late May and early June.
Two types of leaf injury may result from sycamore anthracnose
infections. One type, usually referred to as early leaf blight re-
suits in the complete killing of very young leaves during April or
May. This type of infection may cause partial to complete defolia-
tion and is sometimes confused with frost damage.
The second type of anthracnose injury occurs as small to large
irregular brown areas in the region of the midrib and lateral veins*
of mature leaves. These infections usually do not result in defolia-
tion.
Anthracnose will sometimes cause the formation of cankers on
small twigs an inch or less in diameter. Anthracnose cankers will
sometimes entirely girdle and kill infected branches.
Sycamore anthracnose or blight is caused by the fungus Gnomonia
veneta which lives from season to season in fallen infected leaves
and in twig cankers. Infection is caused by spores of the fungus
which are produced in the spring and washed by rains or carried by
air currents to the young unfolding leaves, where they cause infec-
tion.
Frequent rains and cool temperatures favor the rapid spread of
sycamore anthracnose. Usually, sycamore blight will not cause ser-
ious damage to the trees and merely results in an unsightly appear-
ance for a few weeks until the trees put out a new crop of leaves
in late June or early July. However, repeated annual outbreaks will
eventually so weaken the tree that it becomes suceptible to winter
injury and attacks by borer insects. For this reason, control mea-
sures are rarely attempted except for valuable shade or ornamental
trees.
Homeowners, who wish to prevent development of blight on syca-
more, especially prized as shade trees, may follow the following suggestions:

PURDUE UNIVERSITY Agricultural Extension Service, Lafayette, Indiana
Department of Botany and Plant Pathology, Life Science Building