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Fraser Fir Root Rot Induced by Phytophthora citricola. H. D. Shew, Graduate Research Assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650. D. M. Benson, Associate Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Plant Dis. 65:688-689. Accepted for publication 26 May 1981. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-688.

Phytophthora citricola was isolated from a Fraser fir seedling in a Christmas tree plantation in Avery County, NC. Pathogenicity was demonstrated on 1- and 4-yr-old fir seedlings in greenhouse tests using P. citricola zoospores and infested oat grain inoculum. Fir seedlings developed root necrosis, leaf chlorosis and necrosis, and wilting of new growth 1014 days after inoculation. A zoospore concentration of 104 zoospores per plant caused 40% mortality of 1-yr-old fir seedlings. Propagules of P. citricola recovered from infested soil included sporangia, encysted zoospores, and oospores.