Disease name: Phomopsis tip blight and Kabatina tip blight
Pathogen name: Phomopsis juniperovora and Kabatina juniperi (fungi)
Hosts:
The two most common juniper tip blight diseases are Phomopsis tip blight, caused by Phomopsis juniperovora and Kabatina tip blight, caused by Kabatina juniperi. These are common diseases 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 Phomopsis can infect arborvitae, cedar, European larch, jack pine, and Douglas-fir; Kabatina is mainly a disease of junipers.
Phomopsis tip blight is mainly a leaf and shoot infection that affects the new, young foliage of junipers. The first symptoms are yellow spots on new, young needles. The fungus then enters young stem tissue causing dieback of the new shoot tips. Infected 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.
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 dieback.
Phomopsis tip blight overwinters as spores in the stems of infected plants. In spring, the spores are spread by splashing rain, wind, insects, or mechanical means. Repeated infections occur when temperatures are between 70 to 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 overwinters in newly infected stems. The primary infection period for the Kabatina fungus is autumn. 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.
Cultural management:
When planting, avoid heavily shaded areas and space plants to allow for good air circulation. Avoid wounding plants, especially in spring and fall. Avoid excessive pruning or shearing. Water plants in the early morning so the 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 cultivar.
Resistant cultivars:
There are cultivars that are resistant to Phomopsis and Kabatina tip blight.
Chemical management:
Fungicides are available for management of these diseases.
The pesticide information presented in this publication is current with federal and state regulations. The user is responsible for determining that the intended use is consistent with the label of the product being used. The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement made by The Morton Arboretum.
For current pesticide recommendations, contact The Morton Arboretum Plant Clinic (630-719-2424 or plantclinic@mortonarb.org).
.