Common Tree Issues


This is most commonly seen on white oak and ash trees, especially after cool and wet spring weather conditions. It is a leaf spot caused by a fungus that results in irregular patches of dead leaf tissue, leaf wilting, and premature leaf fall. Anthracnose is essentially a cosmetic problem and does not cause a significant impact to the tree. These two pictures show typical anthracnose symptoms on white oak.

Diseased tree leaf
Diseased tree leaf

Apple Scab
This is most commonly found on apple and crab apple trees. It is a leaf spot caused by a fungus. Leaves are covered with dark-green to black spots and fall prematurely. Apple scab occurs in spring and continues if moist conditions persist. Many disease resistant crab apple varieties are now available for planting.

Apple Scab
Apple Scab Leaf

Fire Blight
This is common to mountain ash, apple, hawthorn, crab apple, and other fruit-bearing plants. Leaves, twigs, and blossoms wilt and turn black as if they have been scorched by fire.

Fire Blight Leaves
Fire Blight Leaves

These are abnormal growths caused by insects and fungi. Galls vary widely in shape and size and can be found on leaves, flowers, branches, and trunks. Most species of evergreens, deciduous trees, and shrubs are susceptible.

Maple Gall
Trunk Gall

Iron Chlorosis
This is most commonly seen on oak, maple, and river birch. It is usually caused by lack of iron, which results in pale-green to yellow leaf color with leaf veins remaining green. Generally iron chlorosis indicates a root problem rather than lack of iron in the soil.

chlorosis Leaf
Chlorosis Tree


Cytospora Canker

This is most commonly seen on Colorado spruce. It is a fungal disease that kills the cambium layer (inner bark), which causes branch and stem cankers. As cankers enlarge and encircle a branch, needles turn brown and the branch dies. Once a canker has become established in the main stem, food and water are cut off, and death occurs above that point.

Cyto Canker
Cyto Canker Branch

Rhizosphaera Needle Cast

This is most commonly found on lower branches of Colorado spruce, especially where trees are growing in groups or rows where airflow is restricted. This needle-cast disease is caused by a fungus that thrives in dark and moist conditions. Needles on lower branches turn brown and fall prematurely, resulting in branch death.

Consult this brochure to diagnose other spruce problems you may have at home.

rhizosphaera-needlecast needles