Arizona cypresses are evergreen conifers. They lack needles, but instead have grayish scales. Gray foliage varieties are more common, but there are many the look more green. In our area they can grow up to 45 feet tall, but they are usually shorter than that for reasons discussed below.
Locally, many trees were planted in the late 1970s and throughout the 1980s. They were cheap, evergreen, attractive and promised to survive in our desert conditions. Having Arizona in the name made them sound even more suitable for our area.
While some wonderful individual specimens of Arizona cypress are found planted throughout the valley, the most common use of this species was planting in rows, particularly as windbreaks or along driveways. This means that most Arizona cypresses are planted in large numbers so if something goes wrong, it does so in a dramatic way!
Our local problems with Arizona cypresses are a result of how this species was used and cared for over the past 3 decades in our landscapes.
This page has information on why these trees are dying, and how to keep them alive.
Along the entire length of the Owens Valley you can find dead or dying Arizona cypress trees. They are easy to find since there are usually a dozen or more trees all in various states of distress.
Arizona cypresses planted as individual specimens as part of a irrigated landscape seem to be doing fine. Trees planted in rows for windbreaks, visual screens next to buildings, or to line driveways are usually the ones we see dying.
In almost every case, the trees were planted too close together. While the trees were young everything was fine. As the trees aged their space and water needs increased.
Irrigation was always applied beginning from when they were planted, or else they would have died almost immediately. The problem is a combination of not meeting the increased water needs as a plant grows, along with the ever-growing competition with its neighbors for resources. Simply, the amount of water and care provided did not keep pace with each trees needs.
A prolonged lack of water and resources creates stress. Stressed trees are susceptible to attacks by pests and pathogens. The widespread decline of Arizona cypress is a result of disease and insects caused by prolonged stress.
A good indicator of the stresses endured by these trees is their small stature. Trees 3 or 4 decades old should be much taller. Most trees I see are well under 30 feet tall, but many are closer to 20 feet in height. Stress slows growth rate.
Both issues thrive in stressed trees. The close planting common here makes it easy for problems to spread along a long, uniform row of stressed plants. Of the 2 bark beetles appear to be more common.
The key to preserving Arizona cypress in Owens Valley landscapes is to reduce stress. Healthy, vigorous trees are less prone to issues.
It may not be an option for you, but mulch can moderate stress and water loss in the roots. Wood chips work well for this purpose.
There are insecticides meant to treat bark beetles. While they can be effective, it usually doesnt make economic sense to treat the large number trees that are usually under attack in your row. It may be worth treating a prized specimen, but unless you take care of the underlying problem of chronic stress, you will not ultimately be successful.
Information on homeowner insecticides used on bark beetles in California is available at this UC IPM page. (Spanish version.)
Arizona cypress trees are widely grown for their ornamental value and ability to thrive in hot, dry climates. However, they can fall victim to certain diseases that affect their health and appearance. Learning how to identify and treat the most common Arizona cypress diseases is crucial for maintaining these handsome landscape trees.
Frequency of Entities
- Arizona cypress tree: 21
- Disease: 16
- Fungal disease: 5
- Infection: 4
- Root rot: 3
- Needle blight: 3
- Pruning: 3
- Bagworms: 2
- Defoliation: 2
- Fungicide: 2
- Cultural practices: 2
- Preventive measures: 2
- Pests: 1
- Canker: 1
- Blight: 1
- Tip blight: 1
- Wilting: 1
- Dieback: 1
- Decline: 1
- Stunted growth: 1
- Insecticide: 1
- Drainage: 1
- Nutrient deficiency: 1
Common Fungal Diseases
Several common fungal diseases can affect Arizona cypress trees, These include
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Cypress Canker – Causes sunken lesions, oozing sap, branch dieback, and foliage discoloration Prune out infected areas and apply fungicide.
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Root Rot – Leads to yellowing leaves, wilting, poor growth, and eventual death. Improve drainage and avoid overwatering. Apply fungicides if severe.
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Needle Blight – Discolors and kills needles prematurely. Prune infected branches and improve air circulation. Use fungicides if needed.
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Tip Blight – Browning and dieback of branch tips during wet weather. Prune affected parts and increase air flow. Consider fungicide treatments.
Symptoms of Disease
Watch for key symptoms that may indicate fungal infections or other diseases:
- Wilting, yellowing, or browning foliage
- Premature leaf or needle drop
- Discolored or oozing lesions on bark
- Dieback of branches and twigs
- Decline in growth and vigor
- Mushy, discolored roots
Pest Problems
Insects and other pests can also damage Arizona cypresses:
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Bagworms – Caterpillars in silk bags feed on foliage, causing defoliation. Handpick bags or use insecticides if severe.
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Borers – Larvae tunnel into bark and trunk, potentially girdling and killing trees. Keep trees healthy to prevent attacks.
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Mites – Microscopic pests feed on sap, turning needles yellowish. Wash off with directed sprays of water.
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Aphids – Sucking insects cause stunted growth. Control with insecticidal soap sprays.
Prevention and Treatment
- Improve air circulation with proper spacing and pruning.
- Promote drainage and avoid overwatering.
- Apply preventive fungicide spray before rainy periods.
- Prune out infected or dead branches.
- Fertilize appropriately to avoid nutrient deficiencies.
- Use integrated pest management for insect problems.
- Remove and destroy heavily infested trees.
- Consult a professional arborist if disease is advanced.
Cultural Practices Are Key
Good horticultural practices go a long way towards preventing Arizona cypress diseases:
- Select disease-resistant varieties when available
- Allow enough space between trees for air movement
- Water early in the day, avoid wetting foliage
- Properly prune trees to improve air flow
- Apply mulch layer to help retain soil moisture
- Monitor for pests and diseases, treat early
- Rake up and remove fallen debris
- Disinfect pruning tools to prevent spread
By properly identifying and promptly treating any diseases, Arizona cypress trees can be maintained in a healthy, attractive state for many years. Stay vigilant for signs of problems and implement good cultural practices for your best defense against cypress tree diseases.
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Common Diseases for Cypress Trees and How We Treat Them
FAQ
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