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Disease Note First Report of Phytophthora Root and Crown Rot of Apple Trees Caused by Phytophthora cactorum in Pakistan. A. A. Shah, Department of Botany, NWFP Agricultural University, Peshawar. S. Hasan, M. Aslam, and I. Ahmad. Department of Botany, NWFP Agricultural University, Peshawar, and Crop Diseases Research Institute, PARC, P.O. Box 1031, Islamabad, Pakistan. Plant Dis. 75:537. Accepted for publication 8 October 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0537A. In the North-West Frontier Province of Pakistan, root and crown
rot of apple (Malus sp.) trees grafted on crab apple MM.106 and
MM.l09 is emerging as a serious problem. Tree losses ranging from
10 to 40% have been reported. In 1987, a survey of apple orchards
in this province showed disease incidence ranging from 0.8 to 13.3%,
with an estimated 3% loss in fruit yield. Isolations from diseased root
and crown tissues using different selective media consistently yielded
only Phytophthora cactorum (Lebert & Cohn) J. Schrot. For testing
pathogenicity, excised dormant apple twigs from four cultivars (Red
Delicious, Valmere, Niggat, and NJ 56) were inoculated (1). Lesions
developed on all the cultivars. Reisolation of P. cactorum fulfilled
Koch's postulates. This is the first report of Phytophthora root and
crown rot of apple trees caused by P. cactorum in Pakistan.
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