Sudden oak death, caused by Phytophthora ramorum (1,2), has been found for the first time in Oregon, killing tanoak, Lithocarpus densiflorus, trees. To our knowledge, this is the first report of the disease outside of the San Francisco to Monterey area in California, (300 km to the south). Nine areas of infestation, all within a 24-km2 area, were discovered on forest lands near Brookings, in southwest Oregon. Mortality centers ranged in size from 0.2 to 4.5 ha and included 5 to approximately 40 diseased trees. P. ramorum was isolated from stem cankers using Phytophthora-selective medium. Isolates had distinctive morphological features characteristic of P. ramorum, including abundant production of chlamydospores and caducous, semipapillate sporangia on solid media. Internal transcribed spacer (ITS) sequences of isolates of P. ramorum from Oregon were identical to ITS sequences of isolates from California (1). The pathogen also was isolated from necrotic lesions on leaves and stems of native Rhododendron macrophyllum and Vaccinium ovatum growing beneath diseased tanoaks. In July 2001, the disease was located by an aerial survey conducted cooperatively by the USDA Forest Service and Oregon Department of Forestry. All lands within 1.6 km (1 mile) of the mortality centers are subject to Oregon quarantine, which bars the transport of any host plant materials. An eradication effort is currently underway. Symptomatic plants and all known host plants within 15 to 30 m of symptomatic plants are being cut and burned in the first phase of this operation. The total treated area is approximately 16 ha. References: (1) D. M. Rizzo et al. Plant Dis. In press. (2) S. Werres et al. Mycol. Res. 105:1155, 2001.
Many Douglas-fir plantations along the north coast of Oregon are exhibiting severe symptoms of Swiss needle cast disease (SNC). These symptoms include premature loss of foliage, abundant fungal pseudothecia on needles, yellowing of foliage, and apparent reduction in diameter and height growth. The development of the disease and its impacts on growth are currently being monitored at three different levels: (l) annual aerial surveys to determine extent of SNC symptoms; (2) plantation surveys to assess the extent of SNC damage and to ground-truth aerial surveys; and (3) intensively measured plots to monitor SNC development and growth impacts.
An epidemic of Swiss needle cast, caused by the ascomycete Phaeocryptopus gaeumannii, is causing defoliation and growth reductions in Douglas-fir forest plantations along the Oregon Coast. The area of symptomatic plantations has been monitored annually since 1996 by aerial survey; in spring 1999, 119,500 ha were affected. Pathogen and symptom development have also been monitored on nine permanent plots in stands of differing disease severity. Infection levels and symptom severity are greatest in low elevation plantations close to the coast. In areas of severe disease, trees retain only current year needles. Defoliation is proportional to the number of stomata occluded by pseudothecia of the fungus, with needles being shed when about 50% of stomata are occupied, regardless of needle age. Fungus sporulation and premature needle abscission are greatest on the upper branches of trees. Annual application of fungicides increases needle retention significantly. Tree height and diameter growth and total tree volume are reduced by disease, and tree volume is significantly correlated with needle retention on our plot trees. The epidemic continues to be most severe in Douglas-fir plantations established on sites where Sitka spruce and western hemlock or red alder predominated in earlier times.
Sudden oak death (SOD) caused by Phytophthora ramorum was first discovered in Oregon forests in July 2001. There appear to have been three separate introductions of P. ramorum into Oregon; in approximately 1998, 2008, and 2014. The most recent of these was the EU1 clonal lineage; all others were the NA1 clonal lineage. Since 2001 an interagency team has been attempting to eradicate the pathogen though a program of early detection (aerial and ground surveys, stream baiting) and destruction (herbicide treatment, felling and burning) of infected and nearby host plants; the program has evolved over time. Post-treatment monitoring indicates that although the pathogen has been eliminated from many of the sites, spread continues. From 2001 to 2015 the quarantine area expanded from 23 km2 to 1,333 km2, where it remains to date. Within a 145 km2 Generally Infested Area near the center of the quarantine area, most sites have not been treated and the disease has been allowed to intensify and spread. Where eradication treatments have stopped, canopy tanoak mortality increased from nearly zero to 87 percent during the 2012-2016 period. Managing sudden oak death in Oregon forests is challenging for many reasons and Oregon’s program is likely to change in the future.
Since the discovery of Phytophthora ramorum in southern Oregon forests in 2001, newly infested areas are located each year. We tracked the spread and dispersal using DNA fingerprinting. While among site genetic variance was low, we did find changes in genotype presence and frequency at the site level. These genotypic differences allowed us to map the spread of some individual genotypes demonstrating long and short distance dispersal of P. ramorum in Oregon Forests.
Pacific madrone (Arbutus menziesii Pursh, Ericaceae) is an important evergreen hardwood species in Pacific Northwest (PNW) forests that provides food and habitat for wildlife and has high value in urban environments. Reeves (2007) indicates that Pacific madrone provides habitat for numerous wildlife species, especially cavity-nesting birds. Its evergreen foliage provides browse, especially in the winter, for a number of animals. The berries are an important food for deer, birds, and other small mammals because they are produced in large quantities and may persist on the tree in winter when alternative food sources are limited (Dayton 1931). Reeves (2007) also indicates that it provides excellent erosion control and slope stabilization and is highly prized as an ornamental species for its crooked beauty, colorful bark, showy flowers, and brightly colored fruits. Pacific madrone is relatively drought tolerant, which makes it desirable in urban habitats. Native American tribes have also used various portions of this tree for food, utensils, and medicinal purposes (Arno et al. 1977, Dayton 1931).
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
