Hemlock Tree Disease Symptoms

Leaf Spot

• Leaf spot is a hemlock disease caused by the Gnomonia caryae pathogen. This disease adversely affects the needles of hemlock trees. It causes rust-colored, irregular spots on the tops of the pine needles and brown spots on the underside. If the condition is severe, the needles drop off the branches. The only treatment for this pathogen is raking up the diseased needles in the fall and removing them from the area to help prevent leaf spot from reoccurring in the spring.

Microstoma

• Microstoma, also known as downy and white leaf spot is a hemlock tree fungus causing varying sizes of yellow spots on the top of the pine needles. The undersides of the needles have white, powdery spots. This disease occurs from the Microstoma juglandis fungus. If the disease becomes too severe, the ends of the branches form short clusters of shoots with undersized needles, known as witch’s brooms.

Mold

• Botrystis is the most common mold that affects the seeds of hemlock trees. The mold causes slow or reduced seed germination, preventing hemlock seedlings from taking root.

Root Rot

• Three root rot diseases in hemlocks are Rhizina undulate, Cylindrocladium scoparium and Fusarium moniliforme, according to the University of Wisconsin. These fungi grow in wet soil and cause severe root damage. Symptoms of root rot in hemlocks include death of the lateral roots that grow off the main root, causing them to blacken and the outer layer of the root to slip off. Root rot eventually causes the pine needles to turn brown.