The Purdue Plant and Pest Diagnostic Laboratory

Phytophthora ramorum Blight
(Sudden Oak Death)


Gail Ruhl, Senior Plant Disease Diagnostician, Purdue University

Plant pathogen found in state for the first time at Portage store - IN Department of Natural Resources Press Release - July 31, 2006

Pictorial Guide and Checklist for Identification of Sudden Oak Death (pdf file) - includes sample submission criteria for Indiana - Purdue University

Ramorum Blight (aka Sudden Oak Death) Wanted Poster (pdf file)

APHIS List of Regulated Hosts and Plants Associated with Phytophthora ramorum (pdf file) - as of August 2013

Click here to view a past What's Hot article on Sudden Oak Death (July 2004)

Phytophthora ramorum is the fungus like micro-organism that causes Ramorum blight and sudden oak death (SOD). Phytophthora ramorum was first identified in 1993 in Germany and The Netherlands on ornamental rhododendrons. P. ramorum was isolated in June 2000 from dying trees in California. Since its discovery in North America, P. ramorum has been confirmed in forests in California and Oregon and in nurseries in California, Oregon, Washington and British Columbia. There are programs addressing Phytophthora ramorum in forests settings and in production nurseries.

The disease can produce rapid decline in tanoak (Lithocarpus densiflorus) and in susceptible species of oak (Quercus), characterized by bleeding cankers on the lower trunk of trees. These cankers produce a sticky, very reddish substance. Mortality appears less likely with other plant species. Damage from SOD in Rhododendron, Vaccinium ovatum and Arbutus menziesii typically involves leaf spotting, cankers on small branches and stems, and/or stem dieback.

The spread of SOD likely occurs through infected plant material, rainwater, and soil. Foliar hosts may play an important role in the transmission of P. ramorum to bark canker hosts. Moist, cool, windy conditions are thought to spread the pathogen by dispersing spores from the leaves of foliar hosts.

At present, the entire host range of this pathogen is unknown. However, Phytophthora ramorum does naturally infect and kill or injure at least 43 host species (pdf file) and has been recovered from an additional 54 plant species. Although many species of Phytophthora are considered common or established in Indiana, P. ramorum is NOT one of them.

On July 31st, 2006, Phytophthora ramorum was reported by Dr. Robert Waltz, IDNR Director of the Division of Entomology and Plant Pathology to have been confirmed by the U.S. Department of Agriculture Animal and Plant Health Inspection Service, Plant Protection Quarantine (USDA APHIS PPQ) on a sample submitted from a Viburnum (a common shrub) located in the garden section of a hardware store in Portage, Indiana. The infected sample was shipped to the store from an Oregon-based supplier.

The plants have been removed from the site and buried deep in a landfill, per USDA APHIS PPQ protocols.

The introduction of this pathogen to Indiana is a cause for concern, not alarm. Our goal is to keep this disease from becoming established in our Indiana landscapes and forests, and the best way to achieve this goal is to educate the public about this disease.

Due to P. ramorum's broad host range and non-descript symptoms, trees and shrubs infected with the pathogen are difficult to distinguish from those with other diseases. Use the checklist provided on this website to help determine if a sample should be submitted for further evaluation.

For more information on Sudden Oak Death, please see our links below.

Government Links/Regulatory Info

University Links

Other Links

Fact Sheets/Articles


State Detection Plans for Phythophthora ramorum

Consult the North Central IPM Center’s Web site at for examples of existing state Phythophthora ramorum detection plans for homeowner plants, as well as some helpful Web resources.












Symptoms on Viburnum

Photo courtesy of Jennifer Parke, OR

Symptoms on Pieris japonica
Photo courtesy of Oregon
Department of Agriculture

Symptoms on Rhododendron
Photo courtesy of Oregon
Department of Agriculture

Symptoms on Rhododendron

Symptoms on Rhododendron

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service