Disease Note.

First Report of Phytophthora Root Rot of Parsley. R. M. Davis, Department of Plant Pathology, University of California, Davis 95616. C. Q. Winterbottom, and S. M. Mircetich, Department of Plant Pathology, University of California, Davis 95616, and J. Valencia, Cooperative Extension, Modesto, California. Plant Dis. 78:1122. Accepted for publication 20 July 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-1122D.

A severe root rot of Italian parsley (Petroselinum crispum (Mill.) Nym. ex A.W. Hill) caused yield losses ranging from 10 to 25% in individual commercial fields in Stanislaus County, California in 1993. Symptoms included wilting, stunting, and a general yellowing of the foliage. Infected primary roots were light to dark brown, while feeder roots were sparse to absent. Phytophthora cryptogea Pethybr. & Lafferty was consistently isolated from infected root tissue on PARP. To complete Koch's postulates, 6-wk-old inoculum of one isolate of the fungus, produced on vermiculite amended with V8 juice and oats, was mixed into a steamed sandy loam soil at a rate of approximately 30 cm3/L of soil. Four- to six-week-old Italian and moss leaf parsley seedlings were transplanted into the infested soil in a greenhouse maintained at 18-25 C. Noninoculated plants served as controls. Half of the inoculated and control plants were flooded for 24 hr every 2 wk over a period of 5 wk. In two separate experiments, all inoculated plants, regardless of flooding treatment, developed symptoms similar to those seen in the field. Most of the inoculated plants within the flooding regime died within 3 wk after inoculation; control plants remained symptomless. P. cryptogea was reisolated from the infected roots, and the reisolates were morphologically identical to the original isolate. This is the first report of a Phytophthora root rot of parsley.