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Brende & Lamb
Trees & Shrubs the Natural Way
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SOD Frequently Asked Questions
Updated 4/1/06
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Recommendations
The best defense against a range of plant pathogens and insect pests is to promote tree health. The following are some general guidelines.
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Prevention
Preventing the movement of infected leaves, wood and soil will be critical to slowing the spread of the fungus to other oak woodlands, such as the Sierra Nevada. Plant material and soil should not be moved from coastal areas. Any wood already moved elsewhere should be burned. Visitors to coastal forests should clean their tires, shoes and animals' feet thoroughly before leaving the area. Construction workers should wash equipment well and should not move dirt from one place to another. Ornamental plants, such as rhododendrons, that may be hosts should not be moved from infected counties unless certified to be free of the pathogen.
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Irrigation
Avoid frequent irrigation of oak trees. Oaks are adapted the dry Mediterranean climate that prevails in central coastal California and most established oaks do not require supplemental irrigation except under severe drought conditions. Consult with a certified arborist or other specialist for advice if extreme drought conditions occur.
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Root zone management
The root zone, the area under the crown + 1/3, is the most vulnerable part of oaks and should be treated as a ZONE OF NO DISTURBANCE. Do not damage the roots by activities such as paving and soil compaction. Apply a 4 - 6 inch deep layer of mulch under the tree canopy. Make sure that the mulch is at least two feet away from the root crown (the area where the trunk fans out to the roots).
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Pruning
Prune dead and dying branches, or others needed to maintain a safe canopy structure, in the dry summer months (June - September) when the activity of both fungus and insects are at a minimum.
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Fertilization
Fertilize if the tree shows external symptoms of deficiency, such as yellowing of the leaves, and the deficiency is confirmed by a laboratory test. Injury Protect the stem and lower limbs from injury.
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Symptomatic Individual Trees in a Garden Setting
Monitor oaks in urban settings for the bleeding symptom year round. If the bleeding symptom is detected, seek confirmation that the cause is the new Phytophthora species.
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CAUTION Not all bleeding on oak stems and limbs is indicative of Sudden Oak Death.
Other causal agents such as Phytophthora cinnamomi, wet wood, sycamore borer, or carpenter worm, may be responsible. Consult with a certified arborist or your University of California Cooperative Extension office for confirmation of the new species of Phytophthora.
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At this time there is no known cure for Sudden Oak Death. A number of compounds are being tested experimentally, but current data are insufficient to warrant the recommendation of any pesticide treatments.
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Symptomatic Trees in Woodland Areas
There is no feasible treatment for trees in a woodland setting. Widescale use of chemicals in these environments is undesirable due to known and unknown negative impacts on native ecosystems. It is hoped that some trees will be resistant to, or tolerate, the pathogen. Some trees may escape infection.
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Advanced Symptoms (dying trees)
Trees with large accumulations of beetle boring dust and growth of Hypoxylon fruiting bodies around the stem base are dying and cannot be saved. Consult with a certified arborist about the extent of these symptoms and the need for tree removal. CAUTION Do not take action until a diagnosis has been made.
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Sudden Oak Death Treatment Recommendations
From University of California Cooperative Extension, Marin County & Division of Insect Biology, University of California, Berkeley
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