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FOLIAGE BLIGHTS OF JUNIPERS AND RELATED CONIFERS
Redcedar severely blighted by Phomopsis juniperovora. Note gray color and hooking of tips of branches.
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| Pathogens: |
Various fungi
Phomopsis juniperovora
Cercospora sequoiae |
| Common Hosts: |
Eastern Redcedars Juniperus virginiana
Southern Redcedars Juniperus silicicola
Italian Cypress Cupressus sempervirens
Arizona Cypress Cupressus arizonica
Related Conifers |
Significance: |
Junipers and related conifers are often severely damaged by a variety of foliage blights. Infections are usually most severe where the foliage of susceptible hosts is subjected to poor aeration or excessive foliage moisture (rain, lawn sprinklers, etc.). In most cases damage is limited to the discoloration and loss of foliage. However, severe infections can result in a substantial disfiguring of infected branches. Infected ornamentals or trees in Christmas tree planting are often rendered so unsightly by foliage blights as to become aesthetically undesirable, resulting in substantial economic losses. |
Recognition: |
Foliage blights are readily identified by the progressive discoloration of infected tissues. Infected foliage first lightens in color to a yellow or yellow-brown and progresses to a red-brown or brown. Infections caused by Phomopsis juniperovora typically begin at branch tips and progress downward and inward. These infections often result in the death of small branches in addition to the death of the foliage. Phomopsis infections are frequently characterized in advanced stages of disease development by ashen gray branch tips that sometimes tend to hook or curl inward. Cercospora infections, on the other hand, generally begin on the inner or lower foliage and progress upward and outward, often leaving tufts of green foliage at the tips of infected branches. Small (less than 1 mm) dark fruiting bodies (sporebearing structures) of the various fungal pathogens can frequently be seen upon close examination of infected plant parts (best seen with a hand lens). Those of Phomopsis appear pimple-like while those of Cercospora appear as dense tufts of minute, hair-like projections.
NOTE: Although the symptoms and signs described are typical of the blights caused by the pathogens indicated, hasty diagnose without laboratory confirmation may lead to faulty identifications. The potential variability of symptoms and the wide variety of fungi capable of causing similar diseases, including many not identified above, make caution an advisable policy. |
Infection Biology: |
Infections occur at all times of the year provided temperatures are warm enough and adequate moisture is available. Spores of the various pathogens are spread by wind, rain, insects, and man. Cercospora infections are limited to foliage tissues, but infections caused by Phomopsis juniperovora involve the woody tissues of small (less than 1 cm) twigs and branches. Conditions favorable to the creation or retention of foliage moisture often dramatically increase the incidence and severity of foliage blight. |
Control: |
The best methods of controlling foliage blights on junipers and related conifers are to promote foliage aeration and to avoid unnecessary watering of foliage (overhead irrigation, lawn sprinklers, etc.). Where practical and cosmetically acceptable, the pruning and discarding of infected plant parts to reduce local inoculum (fungus spores) and prevent disease spread are recommended. The careful application of certain fungicides can provide good protection against infections in certain situations. |
Bulletin No. 196-A | Printed October, 1983 | Contact the
Forest Health Section 
