University of Maryland Extension

Juniper Twig Blights - Phomopsis and Kabatina - Shrubs

close up of phomopsis
Photo: Phomopsis symptoms on juniper

(More diseases of trees and shrubs)

Juniper twig blights caused by the fungi Phomopsis and Kabatina are two of the most damaging diseases to junipers in the northeast. Susceptible species include eastern, red, and white cedar varieties as well as Chinese, common, creeping, needle, Rocky Mountain, savin, shore, and Utah junipers. To a lesser degree, these diseases can also infect American and Oriental arborvitae, hinoki cypress, and English yew. There is however wide variation between susceptible and resistant cultivars within these plant groups. Very few plant cultivars are resistant to both diseases. Cultivars resistant to both Kabatina and Phomopsis include Juniperus chinensis 'Phitzeriana aurea' and J. chinensis var. Sargentii 'Glauca'.

(click on photos to enlarge)

symptoms of phomopsis on juniper
Phomopsis on juniper

phomopsis symptoms closeup
Close-up of phomopsis on juniper.

The primary symptom of Phomopsis blight is the browning and dieback of new shoot tips in the spring. Phomopsis blight is caused by the fungus Phomopsis juniperovora. The fungus over winters on previous blighted twigs and bark. Primary infection occurs during cool wet spring weather but occasional fall infection is possible. Spores are produced from small, black fungal fruiting structures on these old blighted shoots. During wet rainy weather, spores are released and splashed onto the new young growth. Older, unwounded shoots are not susceptible. Blighted twigs first turn pale green and are brown by early summer. Shoots are usually killed back to the previous season's wood. Sunken dark lesions called cankers are formed at the junction of live and dead wood.

kabatina blight symptoms
Kabatina blight

kabatina spore close-up
Close-up of kabatina spores

Kabatina blight primarily attacks and kills juniper twigs 1 year or older during warm, summer weather, unlike Phomopsis blight, which usually kills new shoots in the spring. Kabatina blight is caused by the fungus Kabatina juniperi. In juniper cultivars that take on purple colored winter foliage, shoots infected by the Kabatina fungus late in the season will remain green. Blighted shoots eventually turn brown by late winter and provide a source of infection during the next growing season. Small, black fungal fruiting bodies that produce infective spores form on the blighted twigs. During wet weather, spores are released and washed onto additional stems and twigs. Kabatina requires a small wound to invade the plant usually caused by insect or mite feeding, abrasion by adjacent branches, winter damage or pruning cuts.

Management Strategies: Removal of old dead twigs and branches is very important for the control of both diseases. Previously infected dead shoots should be removed early in the spring before new growth begins to lessen the number of infective spores. The best management option is to select resistant juniper cultivars, however, few cultivars are resistant to both diseases.

Phomopsis blight can be controlled with registered fungicides if applications are made before new growth starts in the spring and continued as long as new growth is produced. However, at present, there are no fungicides effective for Kabatina blight.

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