Juniper tip blight is a common disease of junipers found in most states east of the Mississippi River. There are many varieties of junipers susceptible to tip blights; however, the disease is most serious on young or newly transplanted plants. As the plant matures, disease susceptibility and severity decreases. Occasionally it can infect arborvitae, cedar, European larch, jack pine, and Douglas-fir. The two most common juniper tip blight diseases are Phomopsis juniperovora (Phomopsis tip blight) and Kabatina juniperi (Kabatina tip blight).
Phomopsis tip blight
Phomopsis tip blight, sometimes referred to as juniper twig blight, is mainly a leaf and shoot infection that affects the new, young foliage of junipers. The first symptoms, yellow spots on young needles, may occur 3-5 days after infection. (Sometimes older needles may also show spotting.) The fungus then enters young stem tissue causing dieback of the new shoot tips. Affected foliage turns dull red to brown and then ash gray. As the disease progresses, small lesions (cankers) form on the stems where infected and healthy tissue meet. Eventually the entire branch may die. Infection is spread primarily by splashing rain, wind, insects, or mechanical means. Repeated infections occur when temperatures are between 70 - 80 degrees F, during periods of high humidity, and when foliage is wet. The fungus can persist in dead parts of infected plants for as long as two years.
Kabatina tip blight
Kabatina causes symptoms very similar to Phomopsis, but usually only infects twigs a year or more old. This fungus does not infect healthy foliage, but enters through wounds caused by pruning, insects, or severe winter weather. The first symptoms, dull green then red or yellow discoloration of branch tips, appears in February and March, well before symptoms of Phomopsis tip blight appear. As the disease progresses, spores are formed in the small, ash-gray lesions (cankers) found at the junction between infected and healthy tissue. The brown, dried foliage eventually drops from the plant in late May or June. Kabatina tip blight occurs only in the early spring and does not cause extensive branch die back. The primary infection period for the Kabatina fungus is autumn, even though symptoms are not apparent until late winter or early spring.
Although Phomopsis and Kabatina blights cause almost identical symptoms, their stages of development and control differ. Therefore, it is important to distinguish between the two.
- Plant trees and shrubs that are resistant to Phomopsis and Kabatina tip blight.
- When planting, avoid heavily shaded areas and space plants to allow for good air circulation.
- Avoid wounding plants, especially in spring and fall.
- Water plants in early morning so foliage will dry during the day.
- Prune out diseased branch tips during dry summer weather and destroy.
- If the infection is severe, removal of the plant may be necessary. Replace with a resistant tree selection.
- Avoid excessive pruning or shearing.
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