Juniper Juxtaposition - Kabatina VS Phomopsis

DISEASE DIGEST
Author(s): 

Nancy Taylor, Director of C. Wayne Ellett Plant Pest Diagnostic Clinic, reported receiving a juniper sample with the KABATINA TIP BLIGHT FUNGUS, caused by the pathogen Kabatina juniperi.  Nancy indicated that the Kabatina fungus and resulting symptoms are often confused with Phomopsis tip blight, caused by the fungal pathogen Phomopsis juniperovora.  Nancy taught the assembled group on the BYGL conference call the easy way how to distinguish between Kabatina & Phomopsis tip blights on junipers.

The Kabatina fungus attacks juniper tissue that is at least one-year old or older.  The primary infection period of the juniper tissue, seems to occur in the fall and then foliar symptoms begin to appear in February and March.  The infected tissue first turns chlorotic, then necroses, dessicates, and eventually drops off of the plant in late-May to early June.  The fungus seems unable to penetrate and attack healthy tissue, but prefers wounds or compromised tissue, caused by insect feeding, mechanical damage (mowers, string trimmers, etc.) and weather related incidents (hail, snow or ice loads bending branches, etc.).  Kabatina tip blight often appears randomly scattered on the plant and to be restricted to just branch tips, rather than causing extensive branch dieback or tree death.

On the other hand, the Phomopsis fungus will only infect the current season's new growth and succulent branch tissue of junipers from mid-April through September. The older, mature foliage is resistant to infection by the Phomopsis fungus; therefore, most of the damage or blight will occur on the terminal 4-6" of the juniper branches.  The infected foliage first turns a dull red or reddish-brown, then desiccates fully to become ash-gray in color.  The area of infection can continue to expand or move down the young, succulent branch throughout the summer.

The best way to avoid these fungal blights would be to plant Kabatina and Phomopsis resistant junipers.  To minimize the impact on susceptible junipers, space plants far enough apart to allow for excellent air movement to rapidly dry the foliage.  Avoid shearing these plants or incurring any wounds or damage to the branches by typical horticultural practices, like mowing or using string trimmers to edge landscape beds with juniper plants.

Again the recap knowledge nugget, if the tissue death is on the new season's growth, then it is most likely the Phomopsis tip blight fungus causing the problem.  If the tissue death is on last year's growth or older tissue, then it is most likely the Kabatina tip blight fungus causing the problem.  To determine the actual pathogen or fungus causing the juniper dieback, a sample will need to be sent to the diagnostic lab for microscopic analysis.