Phytophthora Root Rot and Stem Canker of Peach Trees in Mississippi. Robert A. Haygood, Extension Plant Pathologist, Mississippi State University, Mississippi State 39762. Clinton H. Graves, Professor, Mississippi State University, Mississippi State 39762, and William H. Ridings, Professor, Clemson University, Clemson, SC 29631. Plant Dis. 70:866-868. Accepted for publication 13 February 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-866.

Symptoms of Phytophthora root rot and stem canker were initially detected in Mississippi peach orchards in 1982. Incidence ranged from 1 to 75% of trees in the orchards surveyed. During the following 3 yr, Phytophthora cinnamomi, P. cactorum, and P. nicotianae var. parasitica were isolated repeatedly from young, necrotic peach roots. Isolates of all three species, after inoculation to trunks of 1-yr-old container-grown peach trees, caused cankers similar to those observed in the field and also induced root necrosis of peach trees grown in artificially infested soil. This is the first report demonstrating the involvement of P. nicotianae var. parasitica in root and stem canker of peach trees.