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Cypress Tree Problems
By: John Karlik, Environmental Horticulture Advisor

Topics: trees, Cypress, landscaping, gardening, agriculture
Posted by Sharon123 Mon Dec 10, 2007 14:08:14 PST
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Several cypress tree species are frequent in Kern County landscapes and windbreaks.  In recent years significant numbers of cypress appear to be declining, which is likely due to the inherent adaptability of these trees to the local climate.  Certain opportunistic pest problems may accelerate their demise.

Arizona cypress, Cupressus arizonica, and Leyland cypress, Cupressocyparis leylandii, have been extensively planted throughout Kern County.  These species are often found in windbreak plantings around houses or corrals.  Arizona cypress has been widely established in Mojave desert landscapes in the Ridgecrest, Rosamond, and Mojave areas, while Leyland cypress has been planted in Tehachapi and on the San Joaquin Valley floor.  Both species possess cold tolerance sufficient for almost any Kern County location.  Arizona cypress is considered to be drought tolerant based on its performance in desert areas.  When vigorous, these cypresses have few pest problems.

In recent years a number of these trees appear to be declining or have died.  In almost all situations plants have apparently been adequately irrigated.  For Arizona cypress, tree ages at decline are about 20-30 years.  These trees appear to be nearing the end of their natural life span in the desert, but their decline may be accelerated by bark beetle attack.  Although trunk sprays of insecticides may forestall beetle attacks, insecticides are a distant third line of defense – after keeping plants vigorous (especially by supplying sufficient irrigation) and preventing injury (such as from sunburn) which are far more effective strategies.

For Leyland cypress, the fundamental problem appears to be an inherent lack of adaptation to the warm, dry climate of Kern County.  This weakness renders the species susceptible to attack by a canker disease, resulting in a life expectancy of 12-15 years. It has not been uncommon to see entire rows of Leyland cypress turn brown en masse, almost as though a clock had struck their death knell, and this despite sufficient irrigation and appropriate maintenance.  Fungal pathogens such as cypress canker, Seridium or Coryneum cardinale, causes lesions to form on small branches, resulting in death of branch tips, often followed by colonization of larger-diameter wood.  Fungicides cannot be expected to provide any control of this disease, and are not recommended.  Although Leyland cypress trees grow rapidly and provide an excellent screen, their short life expectancy must be considered if they are selected for planting.

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