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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.
>Reference: (1) Z. Borecki and D. F. Millikan. Phytopathology 59:247, 1969.