Reports on Sudden Oak Death don’t seem to be nearly as common as they were a few years ago. The invasive plant disease, which has devastated oak stands along the West Coast, continues to spread in northwestern California and southwestern Oregon. But funding, public engagement, and solutions have been hard to come by.
Fourteen native plant nurseries have joined the California Department of Food and Agriculture (CDFA) Best Management Program (BMP) for Ornamental and Native Plant Nurseries. The program also serves 14 ornamental nurseries. The discovery of Phytophthora tentaculata infecting several native plant species in nurseries and restoration sites has alerted the industry to the cryptic nature of plant pathogens and how easily they can move into the environment. Although the program has been voluntary to date, with the nurseries choosing which BMPs to employ, CDFA and the National Ornamentals Research Site at Dominican University of California are working to identify minimum requirements for acceptance into the program for ornamental interstate shipping nurseries as well as native plant nurseries. CDFA is developing a website to further support the BMP Program.
Native plant nurseries in Washington interested in participating in a multistate research program in 2015-2016 are encouraged to contact Marianne Elliott (email@example.com) for information. The program will investigate the movement of Phytophthora species among nurseries, restoration sites, and forests.
The Kitsap County botanical garden found to have a P. ramorum-positive Pieris plant in April had additional positive plants found in May during the delimitation survey. All infected plants were destroyed and trace-back investigations are underway. The facility will undergo a Critical Control Point Assessment (CCPA) at which time best management practice (BMP) mitigations will be identified for implementation. The BMPs will be enforced through a state compliance agreement. Federal regulatory oversight will continue to ensure the pathogen is being managed effectively.
Five new Phytophthora ramorum hosts were detected during a rare plant survey in February on Marin County Municipal Water District property when unusual Arctostaphylos symptoms were identified. Samples submitted to the California Department of Food and Agriculture (CDFA) Plant Pest Diagnostics Lab tested negative for root pathogens, but the leaves and branches tested positive for P. ramorum. Follow-up official samples were collected for testing by CDFA scientists, which resulted in the identification of five new P. ramorum hosts: Arctostaphylos virgata, Arctostaphylos glandulosa, chinquapin (Chrysolepsis chrysophylla), blackberry (Rubus ursinus), and chaparral pea (Pickeringia montana). Arctostaphylos virgata and Arctostaphylos glandulosa symptoms include leaf spots and necrosis, petiole dieback, stem lesions and cankers, and tip dieback. Many plants of both species were showing symptoms. Chinquapin (Chrysolepsis chrysophylla) symptoms include canopy dieback, leaf spots, and vascular discoloration. Many chinquapin were showing symptoms; two trees were confirmed positive. Blackberry (Rubus ursinus) symptoms include leaf spots and stem lesions. Chaparral pea (Pickeringia montana) symptoms include leaf spots, stem lesions, and thorn dieback. CDFA scientists are in the process of obtaining healthy container plants of each host species to confirm pathogenicity. A follow-up site visit to the water district is planned for July to observe disease progression on these hosts.
Vaccinium parvifolium (red huckleberry) was found P. ramorum positive for the first time from two samples taken at a Lewis County, WA interstate shipping nursery during their 2015 spring Federal P. ramorum Certification Program survey. The Lewis County facility was also positive in 2014 and had undergone a CCPA as well as extensive mitigation activities. A new CCPA has been conducted to determine possible ways the pathogen has continued to infect plant material; additional mitigation efforts will completed in 2015. As a result of the new host confirmation, Vaccinium parvifolium will be added to the federally recognized P. ramorum host and associated host list.
From January 1 to June 3, 2015, P. ramorum was reported in 10 nurseries (OR 8, WA 1, VA 1), one commercial landscape (LA), and a botanical garden (WA) in non-quarantine areas.P. ramorum was detected in Camellia (2), Kalmia (1), Mahonia (1), Osmanthus (1), Pieris (10), Rhododendron (40), Viburnum (4), Vinca (2), and soil samples (8). Four of the nurseries ship interstate and are in the USDA APHIS compliance program (started spring, 2014; Federal Order DA-2014-02). The Confirmed Nursery Protocol is underway in all nurseries and no findings were made at trace-forward sites. Detections at the WA botanical garden are in managed landscapes; survey and disinfestation procedures are underway.
Rhododendron and Kalmia samples were collected from two Puget Sound, WA residential landscapes in April as part of a P. ramorum trace-forward investigation from an out-of-state nursery. All samples were negative.
A mature Pieris plant at a Kitsap County, WA botanical garden was found P. ramorum positive. The sample had been submitted to the Washington State University Plant Clinic in Puyallup. Under the direction of the USDA, regulatory sampling was conducted on the suspect Pieris plant, as well as other plants around the botanical garden. Mitigation and management procedures are being identified and put in place to help prevent spread and future introductions of the pathogen into the garden.
Two Washington waterways in Kitsap and Thurston Counties have been found positive for P. ramorum in 2015. Both waterways have been positive in previous years and are downstream from previously positive nurseries. Ten waterways in six counties (Clallam, King, Kitsap, Lewis, Mason, and Thurston) are being monitored this year for the pathogen; no other confirmations have been made.
This webinar will be especially useful to native plant nurseries addressing Phytophthora species. It will be recorded and posted online if you are not able to attend the live session.
A Systems Approach To Producing Healthy Container-Grown Plants
Tuesday, April 28, 2015
10–11 a.m. PDT
Native plant nurseries are becoming increasingly aware of the risk of harboring plant pathogens, especially Phytophthora species, that have the potential to threaten the health of ecosystems. In this webinar you will learn how to apply a systems approach to analyze your nursery production system and identify potential contamination hazards. You will also learn best management practices that will allow you to take corrective action and help ensure the health of your plants. The presenter will be Jennifer Parke, Dept. of Botany and Plant Pathology, Oregon State University.
This webinar is sponsored by the Working Group on Phytophthoras in Native Habitats; the California Native Nursery Network; the University of California Cooperative Extension; and the USDA-Forest Service, Pacific Southwest Research Station.