Alder Tree Decline and Phytophthora Canker in California

A Long Beach, CA community faces decline in 100+ 20-year-old alder trees. One arborist cited untreatable fungus.

Primary issue: Drought-driven decline, worsened by Phytophthora siskiyouensis (quarantined pathogen) and possibly Phytophthora alni (European alder killer, found in Alaska/Colorado).
Symptoms: Upper canopy dieback, dark moist bark spots, wood cankers.

Deep watering during droughts.
Winter fertilization: 10-10-10 at 1 lb per inch trunk diameter.
Contact UC Riverside's Dr. Deborah Mathews (951-827-3864) for sample submission if similar symptoms appear.

Cold-climate P. alni hopefully won't threaten California plantings.

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