Sudden Oak Death in Washington State

What is Sudden Oak Death? First seen in early 1990s Two types of symptoms –Canker –Foliar blight Caused by Phytophthora ramorum (Oomycetes) Over 70 plant hosts Most of the outbreak in central coastal CA Dead tanoak in Muir Woods NP, CA Foliar symptoms on Rhododendron

Two distinct diseases caused by Phytophthora ramorum Sudden Oak Death Red oaks, beech, and tanoak Stem lesions beneath the bark girdle and kill tree Cankers often bleed or ooze Can kill adult trees “Dead end” hosts P. ramorum foliar blight/Ramorum blight Non-oak hosts Spots and blotches on leaves & shoot die back Can kill juvenile plants, usually not lethal for mature plants Spreads the disease Slide from the USDA PRED Training Module

Phytophthora spore stages Phytophthora thrives in wet conditions P. ramorum infections initiated by sporangia and zoospores Chlamydospores can persist in soil and leaf litter Sexual oospores are resistant to damage Sporangia containing swimming zoospores ChlamydosporesOospores (P. infestans)

How P. ramorum spreads Water - Wind- driven rain, irrigation, runoff Humans – soil on hiker’s boots and bicycle tires, nursery plants Wildlife

P. ramorum genetics Two mating types – A1 and A2 Three clonal lineages – NA1, NA2, EU1 NA1 and NA2 All A2 EU1 Mostly A1, with a few A2 There is concern about NA and EU populations mating, but this has not been observed

P. ramorum in North American forests Map from Kelly, UC-Berkeley SOD currently found in 14 CA counties and 1 OR county These counties are under quarantine SOD not known to be established anywhere else in N.A. forests Slide from the USDA PRED Training Module

Photo: Marin County Fire Department Sudden Oak Death in California  Tanoak (Lithocarpus densiflorus) and oak species affected  Tree death primarily along urban-wildland interface  Dying trees created hazards for residents  Increased fire hazard in wildland areas from dead trees

Photo: Everett Hansen, Oregon State University  Infested area quarantined and eradication attempted  : infested area decreased or remained the same  2005-present: infested area increasing  Area under quarantine now 166 sq miles SOD in Oregon

Risk of sudden oak death based on P. ramorum climate matching and hardwood forest density in the USA Risk Group III Risk Group II Risk Group I (High) Fowler, G., Magarey, R., Colunga, M Climate-host mapping of Phytophthora ramorum, causal agent of sudden oak death In: Frankel, Susan J.; Shea, Patrick J.; and Haverty, Michael I., tech. coords. Proceedings of the sudden oak death second science symposium: the state of our knowledge. Gen. Tech. Rep. PSW-GTR-196. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture:

Red Oak: Quercus rubra P. ramorum in European forests Photo: DEFRA Beech: Fagus sylvatica Slide from the USDA PRED Training Module These species used as ornamentals in WA Rhododendron ponticum

SOD Risk California and So. OregonEuropeWA and BC Stem canker hosts a major component of some forests (Oaks and tanoaks) Stem canker hosts in some forests Stem canker hosts mostly in urban situations Sporulating host present in overstory (Bay laurel) Sporulating host in understory (Rhododendron) Sporulating host – unknown Present in nurseries Suitable climate on coast and in nurseries Suitable climate, no dry season Suitable climate in western portions of region Heavy tree mortality in some wildland areas

Washington P. ramorum surveys Nursery Forest and stream

What happens when P. ramorum is detected in a nursery

Summary of P. ramorum in Washington Found in nursery stock, not thought to be established in natural or urban landscape APHIS and WSDA conduct annual surveys to inspect production nurseries DNR conducts stream baiting and forest surveys Many plants native to Washington are known hosts Potential for impact on native ecosystem Quarantines may be imposed if detected in landscape Slide by Norm Dart

Recognizing Symptoms  Sudden Oak Death of oaks  Ramorum blight of other hosts  Key to determine if samples should be submitted for P. ramorum testing in Washington  focus on recently purchased (or near recently purchased) camellia, kalmia, lilac, pieris, rhododendron, or viburnum

Symptoms on trees Bleeding cankers Cankers can girdle the tree and kill it Host species in Fagaceae: oaks, beech, tanoak Other Phytophthora spp can cause the same symptoms P. cambivora on Beech P. ramorum on Oak

Similar symptoms Phytophthora root disease and canker Armillaria root disease

Bacterial stem diseases Bacterial wetwood Bleeding stem cankers caused by Pseudomonas syringae

Important hosts of P. ramorum in WA nurseries Rhododendron Camellia Viburnum These genera account for over 90% of the positive finds in Washington nurseries Others – –Pieris –Kalmia

Rhododendron Shoot blight Leaf blotch on pacific rhododendron caused by Phytophthora ramorum. Photo by Oregon Department of Forestry.

P. ramorum symptoms on native rhododendron Rhododendron macrophyllum Shoot diebackFoliar blight Photo: Everett Hansen, Oregon State University Slide from the USDA PRED Training Module

Phytophthora root rot - not caused by P. ramorum Photo: Jay Pscheidt, Oregon State University Root rot of rhododendron Slide from the USDA PRED Training Module

Sun scorch, lesion does not extend down leaf midrib Gray blight can develop on sun scorched Rhododendron leaves Photo: Rich Regan, Oregon State University Leaf necrosis of Rhododendron

P. ramorum on Camellia Photos: Oregon Dept. of Agriculture & Cheryl Blomquist, CDFA Brown lesions: irregular and restricted to leaf tip Slide from the USDA PRED Training Module

 Look for lower leaves that have fallen off Symptoms on camellia Photo: Cheryl Blomquist, CDFA

Sun Scorch of Camellia Brown spot not extending along petiole or midrib of leaf Slide by Norm Dart

Viburnum Viburnum tinus “Spring Bouquet” V. plicatum “Mariesii” V. davidii

Symptoms Stem canker Foliage and shoot blight P. ramorum Botrytis Grey mold

Some other hosts Grand fir Bigleaf maple Pacific madrone Lilac

Should an infected plant be submitted for laboratory analysis?  Plants likely to be infected by Phytophthora ramorum - Rhododendron, Camellia, and Viburnum –Affected plant is on host list and purchased since 2002, –Affected plant is near a recently purchased host plant –Symptoms are consistent with Phytophthora ramorum: Brown leaf spots with diffuse margins Shoot tip dieback

Sample referral and submission  In Washington state Master Gardeners and Extension Agents are asked to submit suspect samples to the WSU Puyallup Plant Clinic  If you determine a sample should be submitted  Download and fill out plant clinic sample form and follow approved procedures ml  Please consult the plant clinic before sending samples

For more information please visit the WSU P. ramorum education webpage: You may also call the WSU Plant Diagnostic Lab at (253) with additional questions relating to P. ramorum diagnostics or if you would like to have a plant tested. Slide by Norm Dart