Disease Note.

First Report of Phytophthora cactorum Causing a Shuck and Kernel Rot of Pecan Fruit. C. C. Reilly, USDA-ARS, Byron, GA 31008. F. F. Hendrix, Jr., and M. W. Hotchkiss. Department of Plant Pathology, University of Georgia, Athens 30602; and USDA-ARS, Byron, GA 31008. Plant Dis. 73:701. Accepted for publication 25 May 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0701A.

Phytophthora shuck and kernel rot is the name proposed for a new disease on pecan (Carya illinoinensis (Wang.) K. Koch) caused by Phytophthora cactorum (Lebert & Cohn) Schroeter. The disease was first observed during September 1988 on maturing fruits of major pecan cultivars in central Georgia and caused losses of 50% or greater. In south and south-central Georgia, the disease was present but less severe. Rotting shucks turned dark brown in 4-6 days, with a distinct margin between necrotic and healthy tissue. The disease usually started at the stem end and progressed distally to encompass the fruit. Pecan kernels were also affected, causing the seed coat to turn dark brown and the endosperm to rot. After 2-3 wk, diseased shucks dried and stuck to the shell. Fruits infected after September had dark brown shucks, but kernels developed caramel-colored patches over 25% or more of the surface and quality was reduced. Koch's postulates were satisfied by laboratory and field inoculations of nut clusters with P. cactorum. Symptoms appeared in 4 days for laboratory inoculations and in 6-8 days for field inoculations.