Control PLANT DISEASES
For Better Farming And Better Living

Mimeo BP 2-2
March, 1959

Anthracnose of Shade Trees
Anthracnose is the name given to a disease that frequently attacks some of the
common Indiana shade trees. Anthracnose appears most frequently on the leaves, re-
sulting in sharply defined, discolored spots, but sometimes may appear on twigs
and small branches.
Almost every year the anthracnose disease appears on the leaves of several
types of shade trees. Shade trees affected by this disease are noticeable by their
ragged leaves, and most homeowners are usually fearful that affected trees will
die. Trees affected by anthracnose include ash, birch, chestnut, elm, maple, oak
and walnut.

Anthracnose of Ash
Anthracnose of ash is caused by the fungus Gloeosporium aribum and produces
large irregular, brown dead areas on infected leaves. The dead areas are usually
most conspicuous along the leaf margins. In most years this disease is neither
abundant nor destructive but trees weakened by repeated infection will be unthrifty
and may be ragged and unsightly.

Anthracnose of Birch
Anthracnose of birch is caused by the fungus Gloeosporium betularium which in
wet years may cause damage to river birch. This disease results in the appearance
of small, round, light brown diseased areas with yellow margins on infected leaves.
Spots caused by birch anthracnose will be approximately 1/8 inch in diameter and
are usually evenly distributed over the surface of infected leaves. Sometimes
these spots run together to form large irregular diseased areas. As is the case
with ash anthracnose the disease on birch is seldom serious but may cause concern
to the home owner.

Chestnut Anthracnose
Anthracnose of chestnut, also referred to as small leaf spot, is caused by
the fungus Narssonina ochroleuca. The spots caused by chestnut anthracnose are
small, oval, depressed and yellow to light brown in color. These spots are usually
1/8-1/4 inch in diameter with red to reddish brown borders. Frequently, several of
these spots may unite to form irregular dead areas which later fall out leaving con-
spicuous holes in the leaves.

Elm Anthracnose
Anthracnose of American elm is caused by the fungus Gnomonja ulmea and is
sometimes referred to as elm black leaf spot. This disease is responsible for the
small, circular to irregular black spots that may appear on the upper surface of
elm leaves early in July. Later in the year the black spots become gray in color
with numerous small pustule-like fruiting bodies scattered over their surfaces.

Oak Anthracnose
Oak anthracnose is caused by the fungus Gnomonia veneta and attacks both the
white oak and the sycamore. On white oak, anthracnose will cause irregular brown

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