Threats to Organic Recycling Programs

Sudden Oak Death

Green highlighted words indicate definitions and links to the glossary.

Background

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 (Pest Alert article--Adobe PDF, 121 KB) that causes the disease known as Sudden Oak Death (SOD). Composting and other organic processing facilities within the quarantined area have been under regulatory scrutiny since 2001 due to the concern that movement of green material, compost, and mulch may spread the disease to other counties in California.

Actions

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 U.S. 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 (CIWMB) 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 is an effective sanitation treatment of SOD was published in 2006 with the Journal of Applied Microbiology and can be viewed at http://nature.berkeley.edu/comtf/pdf/Bibliography/swain2006.pdf.

Resources

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.

SOD Genome and Zones of Infection

• U.C. SOD Monitoring
• U.C. SOD research updates
• Maps of SOD affected areas

Disease Symptoms and UCB Composting Research

• U.C. Cooperative Extension Forest Pathology and Mycology Laboratory

Regulations

• California Department of Food and Agriculture Plant Quarantine Manual
• USDA Animal and Plant Health Inspections Service

Related Articles

BioCycle Magazine--February 2003
(These articles made available courtesy of BioCycle magazine. Subscription required for on-line reading of full issue. Purchase of back issues available.)

• Composting as a Control for Sudden Oak Death Disease--Matteo Garbelotto  pg. 53
• Treating Diseased Green Waste--Pat Paswater  pg. 55.

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Last updated: August 29, 2008