Close-up of Kabatina twig blight on juniper. Penn State Department of Plant Pathology & Environmental Microbiology Archives , Penn State University, Bugwood.org
Affected foliage of a juniper (Juniperus spp.). Bruce Watt, University of Maine, Bugwood.org
Terminal dieback of arborvitae due to Kabatina juniperi. Cheryl Kaiser, University of Kentucky, Bugwood.org
Overview
Kabatina blight is caused by the fungal organism Kabatina juniperi. It results in tip dieback of one-year-old growth, causing death to terminal branch ends. It is a problem of junipers, cypress, and arborvitae in North America and Europe.
Symptoms and Diagnosis
Kabatina symptoms occur in late winter or early spring, generally in February and March when the terminal 2-6 inches of diseased growth turns a dull green or yellow-brown and then red or yellow as the infection progresses. Damage can be confused with winter injury. This disease may also be confused with phomopsis tip blight as both may result in dead tips but symptom occurrence is quite different for the two diseases. Phomopsis blight infection occurs in spring and results in the yellowing and death of new, succulent juvenile foliage. Once the needles are fully green and mature phomopsis is not capable of causing infection. Kabatina, however, can infect mature foliage in the fall, winter, or the following spring.
Life Cycle
The disease survives on infected plant debris as grayish lesions at the base of blighted portions of shoots. Fruiting bodies develop as small black "pimples," numerous in spring and diminish as the season progresses. The spores are moved by rain and irrigation and enter wounds or small openings caused by mechanical damage or insect feeding. The primary infection time is believed to be in fall although symptoms are not apparent until late winter or early spring. (Note: Symptoms of phomopsis tip blight occur in late spring as the new growth develops.)
Integrated Pest Management
1. Sanitation. Prune and destroy infected twigs and branches during dry weather. Avoid unnecessary wounding during wet weather which can provide entry points for the fungus. Damage is restricted to tips and doesn't cause the death of the plant.
2. Good culture. Maintain adequate fertility for the plants but do not over-fertilize. Avoid watering at night when the plants will remain wet all night long.
3. Fungicides. There are no fungicides currently registered to control kabatina blight.
Organic Strategies
Strategy 1 is a strictly organic approach. Using an appropriate organic fertilizer would be a viable organic approach to Strategy 2.