Diseases of Shade
Agricultural Extension Service
The University of Tennessee
Entomology and Plant Pathology
Shade trees and small ornamental trees may be affected
by plant diseases. Most are simply aesthetic problems and
cause no long-term damage to the tree. Some diseases can
seriously disfigure trees, while others are lethal.
Anthracnose diseases attack the foliage and twigs of
trees in late spring and early summer. Cool, wet weather
favors infection and spread of these diseases. Ash, dog-
wood, maple and sycamore may be damaged by anthracnose
diseases caused by a variety of fungi. The canopy of af-
fected trees may be visibly thinned. Angular leaf spots, dead
leaf tissue delineated by veins, twig dieback and cankers on
small branches are common. Repeated defoliation may
weaken trees and lead to death.
◆ Anthracnose diseases of maple and ash occur sporadi-
cally and are seldom a serious threat. Ash anthracnose may
cause 50 percent defoliation within a few days of infection.
◆ Dogwood anthracnose and sycamore anthracnose may
occur annually and weaken or kill infected trees. Dogwood
anthracnose is much more damaging to flowering dogwood
growing as an understory tree in full shade.
◆ Spot anthracnose occurs throughout the range of flow-
ering dogwood. Small, red lesions appear on bracts of flow-
ers and later on leaves. Although, it may deform flowers
and leaves, spot anthracnose does not lead to defoliation
Leaf blister and leaf curl refer to foliar diseases in which
young, expanding leaves are infected. Symptoms include
raised blisters for oak leaf blister and fleshy, distorted leaves
for peach leaf curl. Affected leaves usually remain on the
tree and function normally.
Leaf blotch fungal disease on buckeye.
Alan WindhamSpot anthracnose on dogwood leaves.
Numerous fungal leaf spot diseases affect trees and a
few bacterial leaf spot diseases:
◆ Scab is a disease of crabapple. Olive-brown spots de-