Title: Determining the risk of Phytophthora ramorum spread from nurseries via waterways
Author: Elliott, Marianne; Chastagner, Gary; Coats, Katie; Dermott, Gil;
Source: In: Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. Proceedings of the sudden oak death fifth science symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 55-59
Publication Series: General Technical Report (GTR)
Description: Phytophthora ramorum, the fungus-like pathogen which causes sudden oak death, is a threat to the Pacific Northwest nursery industry. Because this is a quarantine organism, the destruction of plants and mitigation treatments resulting from a positive P. ramorum detection has caused millions of dollars in losses to the commercial nursery industry in California, Oregon, and Washington. There is concern about movement of the pathogen to nurseries and forests in the eastern United States. An increase has been seen in the NA2 and EU1 lineages from nursery samples in Washington in recent years, so a study of the relative fitness of P. ramorum isolates in the Washington State University culture collection was undertaken. Eighty-five isolates were screened for sensitivity to the fungicide mefenoxam and for relative pathogenicity on detached rhododendron leaves. Most isolates of P. ramorum were sensitive to the fungicide with the exception of some EU1 isolates from one nursery and its trace-forwards. A strong relationship between phenotypic characteristics such as fungicide sensitivity and pathogenicity, and the originating nursery, was seen. Since P. ramorum is moving from nurseries into streams, a method for exposing plants to contaminated stream water was tested. Further studies will include measuring inoculum levels in irrigation water from streams to determine whether this pathway is of importance in disease spread.
Keywords: Phytophthora ramorum, nursery industry, mefenoxam sensitivity
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Elliott, Marianne; Chastagner, Gary; Coats, Katie; Dermott, Gil. 2013. Determining the risk of Phytophthora ramorum spread from nurseries via waterways. In: Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. Proceedings of the sudden oak death fifth science symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 55-59.
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