California Department of Resources Recycling and Recovery (CalRecycle) 

Alerts for Organics Recycling Programs

Sudden Oak Death

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Beginning in 1995, coastal region residents noticed that large numbers of oaks and tanoaks were dying in Northern California. Researchers investigated these tree mortalities for several years and discovered a new plant pathogen, Phytophthora ramorum that causes the disease known as Sudden Oak Death (SOD).


The primary mode of disease spread over large distances is probably due to the presence of infected plants in commercial nursery shipments based on the numerous pest detections that have occurred in recent years across the United States and Canada. However, regulatory concern is also focused on the risk of spreading the pathogen in green material from the quarantined area to other California counties. Since it is difficult to determine the plant species of commingled trimmings, green material is subject to regulatory scrutiny even if there is no host material present.

Recognizing the importance of protecting markets for recycled-content products established by local jurisdictions, the California Integrated Waste Management Board (now known as the Department of Resources Recycling and Recovery, or CalRecycle) funded a multi-year, $80,000 research project to examine the effectiveness of the composting process to sanitize SOD-infected materials. The project was conducted in partnership with Steven Swain and Dr. Matteo Garbelotto of the University of California, Berkeley (UCB) and commercial composters. UCB research data was compiled in 2003 for plant quarantine officials' consideration of composting as an alternative treatment for SOD-infected materials. The UCB project results show that the composting process kills Phytophthora ramorum and the associated spores. A UCB final report containing data substantiating composting as an effective sanitation treatment of SOD was published in 2006 with the Journal of Applied Microbiology.


The California Oak Mortality Task Force (COMTF) was formed in August 2000. COMTF is a consensus-driven coalition of educational institutions, public agencies, non-profit organizations and private interests. Its primary purpose is to coordinate research, management, monitoring, education and public policy efforts addressing elevated levels of oak mortality relative to SOD.

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Last updated: May 18, 2011
Organic Materials Management