Anthracnose and Other Common Leaf Diseases of Deciduous ...

Oklahoma Cooperative Extension Service 

EPP-7634 

Anthracnose and Other 

Common Leaf Diseases 

of Deciduous Shade Trees 

Sharon von Broembsen 

Extension Plant Pathologist 

Homeowners are justifiably concerned when foliage of 

their yard trees becomes diseased, especially when these 

diseases cause defoliation, twig and limb death, and perhaps 

death of a tree that has been defoliated several years in a 

row. Concerned homeowners need information on how to 

prevent or otherwise control leaf diseases. This fact sheet 

was produced to help fill this need. This fact sheet describes 

the symptoms and control of leaf diseases of common deciduous 

hardwood trees commonly planted in yards. Diseases of 

coniferous trees (junipers, cedars, pines, etc.) are covered in 

OSU Extension Fact Sheet EPP‐7618, “Common Diseases of 

Conifers in Oklahoma.” Powdery mildew diseases of shade 

trees are covered in OSU Extension Fact Sheet EPP‐7617, 

“Powdery Mildews of Ornamentals and Fruit, Shade, and Nut 

Trees.” Though the pecan tree is sometimes used as a shade 

tree, its leaf diseases are not covered here; pecan leaf disease 

control is discussed in OSU Extension Fact Sheet EPP‐7642, 

“Pecan Diseases: Prevention and Control.” Diseases of fruit 

trees are covered by several OSU Extension Fact Sheets and 

Current Reports. 

Leaf Disease Types 

Leaf diseases of deciduous hardwood trees are grouped 

into six categories, to simplify their identification, as follows 1 : 

Anthracnose—Irregular dead areas on leaf margins, 

between and across and/or along veins, often moving onto 

the shoots and small twigs; sometimes whole leaves are 

engulfed. 

Leaf spot—Dead spot on the leaf that is well defined 

from healthy tissue. 

Leaf blotch—Dead area on the leaf that often diffuses 

into healthy tissues. 

Shot‐hole—Loss of dead areas inside of spots that result 

in a series of holes in the leaf. 

Leaf‐blister—Leaf spot or blotch that is swollen or raised, so 

that the area appears blisterlike on the upper surface of the leaf. 

Powdery mildew—Superficial growth of white to graywhite 

fungus material on leaves and shoots. 

Common Leaf Diseases of Deciduous 

Trees 2 

Anthracnose and Leaf Blotch 

Ash, green, and red (Fraxinus spp.)—The common 

leafspot and scorch on ash leaves is caused by the ash 

1 Tattar, T.A. 1978. Diseases of Shade Trees. Academic Press, Inc., New York, N.Y. 

2 Adapted mainly from Pirone, P. P. 1978. Diseases and Pests of Ornamental Plants. Fifth 

Edition. John Wiley and Sons, New York, N.Y. 

Oklahoma Cooperative Extension Fact Sheets 

are also available on our website at: 

http://osufacts.okstate.edu 

anthracnose fungus, Glocosporium aridum. Large areas 

of infected leaves, especially along the edges, turn brown. 

Premature leaf drop may occur. 

Birch (Betula spp.)—Anthracnose of birch leaves is 

caused by Glocosporium betularum. This fungus causes 

brown spots with dark brown to black margins. 

Maple (Acer spp.)—Anthracnose, caused by the fungus 

Gloeosporium apocryptum, can be serious on sugar and silver 

maples and box‐elder, during rainy seasons. Indefinite light 

brown spots appear early; they may enlarge and run together 

causing death of infected leaves. Partially‐killed leaves appear 

scorched. The sycamore anthracnose fungus, Gnomonia 

Veneta, also infects maple leaves. 

Oak (Quercus spp.)—Anthracnose, caused by the fungus 

Gnomonia quercina, is a common disease of oaks. Rainy 

weather favors infection and defoliation may result. Infected 

areas frequently run together and cause the appearance of 

a leaf blotch or blight. The dead areas follow smaller veins 

and are bounded by larger veins. 

Sweetgum (Liquidambar spp.)—Anthracnose of 

sweetgum leaves is caused by the fungus Gloeosporium 

nervisequum. Infection by this fungus causes black areas on 

the leaves. 

Sycamore and London plane tree (Platanus spp.)— Anthracnose 

of sycamore and London plane tree is caused by the 

fungus, Gnomonia platani (Figure 1). The London plane tree 

is more resistant to anthracnose infection than are sycamore 

trees. Anthracnose is the most serious disease of sycamore. 

The first symptoms appear in early spring as the leaves begin 

to unfurl from the leaf buds, and at this stage the disease 

may be mistaken for frost damage. Infected leaves that do 

not drop will develop light brown dead areas, usually along 

the veins. The spots may enlarge to cover entire leaves and 

cause premature defoliation. 

Walnuts and butternut (Juglans spp.)—Anthracnose, 

sometimes called brown leafspot, is caused by the fungus 

Gnomonia leptostyla (Syn. Marssonia juglandis). Anthracnose 

is a common disease of these trees. Leaflets are infected during 

the summer and irregular brown spots develop. Defoliation 

may result. 

Leaf Spot Diseases 

Ash, green, and red (Fraxinus spp.)—Several leaf 

spot diseases occur on ash, but these are considered to be 

minor. The most common disease in this group is caused by 

Division of Agricultural Sciences and Natural Resources • Oklahoma State University

Figure 1. Symptoms of sycamore anthracnose on a 

mature leaf. 

Photo courtesy of Clemson University Extension Service. 

Figure 2. Symptoms of Septoria leaf spot on a poplar 

leaf. 


Phyllosticta fraxinicola. This fungus causes large, yellowish 

brown lesions with small black spots developing on the lower 

side of infected leaves. Cylindrosporium fraxinihas also been 

reported in Oklahoma. 

Basswood, linden (Tilia americana)—A leaf‐blight, 

caused by the fungus Cercospora microsora, causes circular 

brown spots with dark borders. When the spots are very numerous, 

the entire leaf may turn brown and fall off the tree. 

Catalpa (Catalpa spp.)—Brown leaf spots are caused 

by three species of fungi (Alternaria catalpae, Cercospora 

catalpae, and Phyllosticta catalpae). 

Cottonwood, Lombardy poplar, white poplar (Populus 

spp.)—Leaf spots on Populus trees are caused by a variety of 

fungi of which Marssonia spp. is the most common. It causes 

brown spots and premature defoliation. Septoria spp. have 

also been found (Figure 2). 

Dogwood (Cornus spp.)—Many species of fungi cause 

leaf spots on dogwood. Two species are found in Oklahoma. 

Septoria cornicola causes brown angular lesions, and the 

dogwood anthracnose fungus, Elsinoe corni, causes small, 

reddish spots. 

Elm (Ulmus spp.)—There are many fungi that cause leaf 

spots of elm. The most common one is blackspot (caused by 

Gnomonia ulmea). The first symptoms of blackspot appear 

early in the spring as small white or yellow flecks on the upper 

leaf surface. The flecks enlarge and their centers turn black. 

If infections are heavy, leaves may drop prematurely. Usually, 

the disease becomes prevalent in the fall about the time of 

normal leaf drop and little damage to the tree occurs. Another 

common leaf spot is anthracnose caused by Gloeosporium 

ulmi. Infections by this fungus results in reddish brown spots. 

Hackberry (Celtis spp.)—Many fungi cause leaf spots on 

leaves of hackberry during rainy seasons. These leaf spots are 

seldom serious enough to require a fungicide application. 

Honey locust (Gleditsia spp.)—A leaf spot of honey 

locust is caused by Melasmia gleditsiae (Linospora gleditschiae). 

Numerous black fruiting bodies of the fungus form on 

the lower side of the leaves. 

Kentucky coffeetree (Gymnocladus dioica)—Three 

fungi cause leaf spots on leaves of the Kentucky coffeetree, 

but special control measures are rarely required. 

Magnolia (Magnolia spp.)—Fifteen species of fungi 

cause leaf spots on leaves of magnolia trees. Septoria magnoliae 

is found most commonly in Oklahoma. It causes brown 

lesions. 

Maple (Acer spp.)—Purple‐eye leaf spot caused by Phyllosticta 

minima is characterized by large irregular spots with 

brownish centers and purple‐brown margins. Black fruiting 

structures develop in the center of the spots. The disease is 

most severe on red, sugar, and silver maples. 

The tar spot fungus, Rhytisma acerinum, seldom infects 

street trees, but red maples in forests are frequently infected 

(Figure 3). 

Mulberry (Morus spp.)—Leaves of mulberry trees are 

spotted by two fungi, Cercospora moricola and Cercosporella 

mori, which cause reddish‐brown spots. These diseases are 

most severe during rainy weather. 

A blight of mulberry leaves is caused by a bacterium, 

Pseudomonas syringae pv. mori, which at first appears as 

water‐soaked spots. The spots later become sunken and 

black. The leaves become distorted, and infected leaves on 

the twig tips wilt and die. 

Oak (Quercus spp.)—Leaf spots on oak leaves are 

caused by many fungal species. In Oklahoma, the most common 

one is caused by Actinopelte dryina. Leaf spot diseases 

rarely cause much damage, as they become numerous only 

late in the season. 

Redbud (Cercis spp.)—Redbud has two fungal leaf 

spot diseases in Oklahoma. Each is caused by a Cercospora 

species (C. cercidicola/Mycosphoerella cercidicola and C. 

cercidis). 

Sweetgum (Liquidambar spp.)—A leaf spot disease 

caused by the fungus Cercospora liquidambaris occurs in the 

southeastern states and Texas and may eventually occur in 

Oklahoma. 

Sycamore and London plane tree (Platanus spp.)— 

Brown and angular leaf spots caused by Septoria platanifolia 

and Cercospora platanicola occur on sycamore leaves. 

Walnuts and butternut (Juglans spp.)—Brown leaf spot, 

caused by the fungus Gnomonia leptostyla (syn. Marssonina 

juglandis), is a common disease of walnuts and butternut. 

Leaflets are infected in the summer and develop irregular 

dark brown or blackish spots. Defoliation may result. 

Downy spot or yellow leaf blotch, caused by Microstroma 

juglandis, causes a yellow blotching on the upper side of leaves 

and a matching white coating on the under side of infected 

leaves. 

EPP-7634-

Figure 3. Symptoms of tar spot disease on a maple leaf. 


Figure 4. Symptoms of leaf blister on an oak leaf. 


Leaf Blister 

Elm (Ulmus spp.)—Leaf curl is caused by Taphrina ulmi. 

Infection by this fungus occurs in early spring and results in 

small blisters, which eventually cause abnormal leaf development. 

Oak (Quercus spp.)—During cool, wet springs almost 

all species of oaks can become infected by the leaf blister 

fungus, Taphrina caerulescens. Circular raised areas occur 

on the upper leaf surface, causing matching depressions on 

the lower surface. The raised areas are yellowish‐white and 

the depressed areas are yellowish‐brown (Figure 4). 

Control 

Most leaf diseases of yard trees are controlled by gathering 

and destroying fallen, infected leaves. Where fallen 

diseased leaves have not been destroyed, chemical control 

is the alternative approach. For suggested fungicides, consult 

the current circular E-832, OSU Extension Agents’ Handbook 

of Insect, Plant Disease, and Weed Control. 

During very rainy springs when leaf diseases become 

severe, two to three chemical applications, beginning when 

the leaves are first unfurling from the buds and repeated when 

the leaves are half grown, and again when the leaves are fully 

developed, will usually provide good control. 

Trees that have been affected by leaf diseases every 

season should also be well fertilized and watered to maintain 

vigor. Do not fertilize during early fall. Fertilize only after the 

trees are dormant. 

EPP-7634-3

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EPP-7634-4

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