Phytophthora ramorum in Oregon forests: six years of detection, eradication, and disease spread

Abstract

Phytophthora ramorum was first discovered in Southwest Oregon forests in 2001, where it was killing tanoak (Lithocarpus densiflorus) and infecting Pacific rhododendron (Rhododendron macrophyllum) and evergreen huckleberry (Vaccinium ovatum). At that time there were nine infested forest sites totaling 16 ha. Aerial photographs suggest that P. ramorum probably was killing tanoak trees at one of these sites as early as 1998. In fall of 2001 eradication of the pathogen from infested sites began by cutting, piling and burning infected plants and all host vegetation within 30 to 100 m. of infected or symptomatic plants. Upon completion of burning most sites are planted with non-host or conifer seedlings. After one year it was clear that tanoak stumps sprouted prolifically following treatment and that P. ramorum occasionally was recovered from these sprouts. Follow-up treatments were necessary to destroy residual host material and stump sprouts that potentially harbored the pathogen. In 2003 and subsequent years all tanoaks in treatment areas were injected with herbicide prior to cutting in order to prevent sprouting (except on USDI-BLM lands where herbicide use was banned). Eradication treatments have been completed or are underway on approximately 560 ha of forest land, at a cost of $2.6 million dollars. Nearly all eradication costs have been paid by federal and state agencies, with much cooperation by landowners. There is no compensation to landowners for loss of timber or other values as a result of the eradication treatments.

Parent Publication

• Proceedings of the fourth meeting of the International Union of Forest Research Organizations (IUFRO) Working Party S07.02.09: Phytophthoras in forests and natural ecosystems

Citation

Kanaskie, Alan; Hansen, Everett M.; Goheen, Ellen Michaels; McWilliams, Michael; Reeser, Paul; Sutton, Wendy . 2009. Phytophthora ramorum in Oregon forests: six years of detection, eradication, and disease spread. In: Goheen, E.M.; Frankel, S.J., tech. coords. Proceedings of the fourth meeting of the International Union of Forest Research Organizations (IUFRO) Working Party S07.02.09: Phytophthoras in forests and natural ecosystems. Gen. Tech. Rep. PSW-GTR-221. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 170-172