Hemlock Diseases

Informational table showing disease name, symptoms, pathogen/cause, and management of Hemlock diseases.
Hemlock Diseases - Articles


Cytospora canker Slightly sunken cankers girdle and kill branches. Valsa (Cytospora) Prune infected branches.
Fabrella needle blight Needles in the lower part of the tree turn brown and fall in late summer, leaving bare twigs. Fungal fruiting structures appear as small dots on the underside of the needle, white at first but then darken, lining either side of the main vein. Fabrella tsugae No control is recommended. Generally, little damage occurs unless the tree is under other stresses such as drought or insect attack.
Cone and twig rustCones become covered with dusty, yellowish spores. Twigs twist and die and have yellowish spores on them.Melampsora farlowii No control is recommended for this fungus, which only requires hemlock to complete its life cycle.
Needle rustCurrent-season growth is slightly swollen and curled. Orange-yellow spores coat the infected tissue. Infected plant parts die in the summer. Orange-yellow spores develop on poplar leaves where the fungus over-winters.Melampsora abietiscanadensis (hemlock ↔ poplar)

Pucciniastrum hydrangeae (hemlock ↔ hydrangea)

Pucciniastrum vaccinii (hemlock ↔ rhododendron and others)
No control is recommended for these fungi, which over-winter on the broadleaf host and then spreads to hemlock.

Fabrella needle blight (Penn State Dept. of Plant Pathology collection) From the PA Department of Natural Resources.

Prepared by Gary W. Moorman, Professor of Plant Pathology