Canker Expansion on Water-Stressed Pin Oaks Colonized by Endothia gyrosa. D. N. Appel, Former Graduate Research Assistant, Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061. R. J. Stipes, Professor, Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061.. Plant Dis. 68:851-853. Accepted for publication 19 May 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-851.

The effect of moisture stress on predisposition of 5- to 7-yr-old pin oak (Quercus palustris) grown in containers to canker induction by Endothia gyrosa was studied. Inoculated trees were subjected to episodes of drought in the greenhouse. Only stressed trees were colonized by the fungus. Colonization was consistently inhibited in regularly watered trees, and a callous ridge formed around the inoculated wound. During drying of the potting media, resistance to colonization diminished before wilting was evident. Cankers elongated most rapidly 2–8 days after a drying period was terminated by watering. A target pattern in cankers resulted from repeated episodes of drought.

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