Pacific Southwest

Title: Vegetation response following Phytophthora ramorum eradication treatments in southwest Oregon forests

Author: Goheen, Ellen Michaels; Hansen, Everett; Kanaskie, Alan; Sutton, Wendy; Reeser, Paul

Date: 2008

Source: In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M., tech. coords. 2008. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 301-303

Station ID: GTR-PSW-214

Description: Sudden oak death, caused by Phytophthora ramorum, was identified in late July 2001 in forest stands in Curry County on the southwest Oregon coast where it was killing tanoak (Lithocarpus densiflorus) and infecting Pacific rhododendron (Rhododendron macrophyllum) and evergreen huckleberry (Vaccinium ovatum). Affected stands occurred on industrial forest land, non-industrial forest land, and federal forest land. Treatments to eradicate the pathogen from affected sites were started in the fall of 2001 and consisted at that time of cutting, piling, and burning all infected host vegetation and any known Oregon host species within a 15 to 30 m buffer around all infected plants. While a number of plant species on the official host or associated host lists occurred in Oregon forests, only those plant species that had a history of being infected in Oregon were treated. Patch size of the initial treatment areas ranged from 0.2 to 4.5 ha. Since that time, additional disease centers have been identified and eradication treatments have been completed at every site. Some treatments were adjacent to sites treated previously while others involved distinct new centers. Size of treated sites has varied widely. Over the last 5 years, treatment methods have been altered to reflect increased understanding of host susceptibility and pathogen survival and spread. Additional treatment components have included various combinations, where possible, of backpack herbicide spraying to kill stump sprouts, stump-top treatments with herbicides to prevent tanoak sprouting, injecting all tanoaks greater than 2.5 cm diameter with herbicides to prevent sprouting, raking, piling, and burning all Oregon host material, and increasing buffer width to 100 m. Some sites have been planted with conifer seedlings while others have not. The end result is a mosaic of treatment patch sizes, shapes, and structures including sites where 1) Douglas-fir (Pseudotsuga menziesii) logs were removed from the sites and the tanoaks and understory species were cut and destroyed in broadcast burns, 2) sites where 10 to 20 percent of the conifer overstory remains and he treatment area has been replanted with conifer seedlings, 3) a site where little change has occurred in an old-growth coast redwood (Sequoia sempervirens)/Douglas-fir overstory but more than 90 percent of the midstory and understory trees and shrubs were removed, and 4) small (less than 0.2 ha) openings with non-host mature alder trees left on site.

Keywords: Phytophthora ramorum, sudden oak death, eradication

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Citation

Goheen, Ellen Michaels; Hansen, Everett; Kanaskie, Alan; Sutton, Wendy; Reeser, Paul   2008.  Vegetation response following Phytophthora ramorum eradication treatments in southwest Oregon forests.   In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M., tech. coords. 2008. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 301-303.