New Sudden Oak Death appears on coast

By Oregon Department of Forestry

State officials announced that a new site with trees infected by the pathogen Phytophthora ramorum – also known as Sudden Oak Death – has been discovered in Curry County. The new infection site is over six miles north of a quarantine boundary established by state and federal officials to stop the spread of Sudden Oak Death (SOD) infection outside of southwest Oregon.

Two tanoak trees infected with Phytophthora ramorum were noted by Oregon Department of Forestry insect and disease specialists through aerial detection in Cape Sebastian State Park, about 20 miles north of Brookings. Follow-up survey work on the ground confirmed the diagnosis. Other tanoak trees in immediate vicinity also showed browning of the lower tree crown, which can be an early symptom of Sudden Oak Death.

As required by State law, the Cape Sebastian State Park infection site and a three mile buffer zone are now included in the Sudden Oak Death quarantine area. Plants species susceptible to P. ramorum and soil associated with the infected trees cannot be moved out of the area, unless heat treated to required specifications. Because the site is outside of the existing quarantine boundary, the State is moving as quickly as possible to treat the site to minimize the risk of spread of the pathogen.

State officials are unsure at this point how the pathogen travelled outside the SOD quarantine area established three years ago to contain the spread.

“Additional investigation is needed to determine how this new area – which is over 12 miles from the nearest known infected tree – acquired the pathogen,” said Alan Kanaskie, forest pathologist with the Oregon Department of Forestry. “Once we have determined the extent of the infestation, we will develop a treatment plan and move quickly to complete the work before the onset of autumn rains in the region.”

SOD can kill highly susceptible tree species such as tanoak, coast live oak, and California black oak by causing lesions on the main stem. Tanoak is by far the most susceptible species in Oregon, and the disease seriously threatens the future of this species. The pathogen also causes leaf blight or dieback on many other host plants including rhododendron, evergreen huckleberry and Oregon myrtle. Oregon’s iconic Douglas fir also can be infected by the pathogen but it is not seriously damaged. Early detection of SOD is achieved through a combination of aerial survey, follow-up ground visits and monitoring the presence of the SOD pathogen in streams. These efforts are critical to ongoing attempts to slow spread of the pathogen in Oregon.

Between 2001 and the end of 2009, eradication treatments were completed on approximately 2,900 acres of forest at an estimated cost of $5 million. Despite this effort, SOD continues to slowly expand in Curry County — from 2007 to 2009 approximately 60 new infested sites were found each of the two years.

In 2010, 83 new sites were found, and thus far in 2011 more than 100 new Sudden Oak Death sites have been found. SOD experts presume the increased spread of the disease is due to consecutive years of weather favorable for disease spread, slow development of recognizable symptoms, and delays in treatment application associated with detection and resource constraints.

In 2008, a 162-square-mile quarantine zone for SOD was established in southern Curry County. The quarantine restriction prohibits nursery products, wood products or specialty forest products grown in areas known to contain SOD pathogens from being exported outside the quarantine zone unless specific disease-prevention protocols are followed. The federal Animal and Plant Health Inspection Service (APHIS) and the Oregon Department of Agriculture have programs in place with forest and plant producers in Curry County to ensure these products can continue to be processed and certified as pathogen-free for sale outside Curry County. The quarantine area and rules were revised in 2011.

Sudden Oak Death is a relatively new plant disease in Oregon. It was first discovered in July 2001 at five sites on the southern coast near Brookings, although aerial photos of the area indicate that the pathogen may have been present at one site since about 1997 or 1998. Outside of Oregon, SOD is known to occur only in forests in 14 California counties and in several European countries. The origin of the pathogen is unknown.

There are several ways to help prevent the spread of SOD.

* Buy only certified plant stock from a licensed nursery.
* If traveling in areas with known SOD infestations, clean shoes, vehicles, and pets’ feet when leaving the area.
* Do not gather any plant materials in SOD-infested areas.
* Do not move firewood from an infested area.
* If you suspect a plant may be infected with SOD on your property, call 1 (800) INVADER.

Disclaimer: Articles featured on Oregon Report are the creation, responsibility and opinion of the authoring individual or organization which is featured at the top of every article.