Disease Note

Occurrence of Oak Bacterial Leaf Scorch Caused by Xylella fastidiosa in Kentucky. J. R. Hartman, Department of Plant Pathology, University of Kentucky, Lexington 40546. C. A. Kaiser, U. E. Jarlfors, B. C. Eshenaur, P. R. Bachi, and W. C. Dunwell. Department of Plant Pathology, University of Kentucky, Lexington 40546; Research and Education Center, P.O. Box 469, Princeton, KY 42445. Plant Dis. 75:862. Accepted for publication 4 March 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0862D.

Bacterial leaf scorch of landscape trees, caused by Xylella fastidiosa Wells et ai, has been reported in the Atlantic and Gulf coast states from New York to Texas. In Kentucky, the disease was first identified in three pin oaks (Quercus palustris Munchh.) in Lexington in October 1987. The trees showed premature leaf browning and defoliation, and the leaves had a marginal necrosis. The disease was confirmed by detecting the pathogen with an ELISA test specific for Xylella (Agdia, Inc., Elkhart, IN) and by direct electron microscopic observation of the causal agent in leaf petiole tissues. The bacterial cell wall was scalloped or rippled, which is typical for this xylem-limited bacterium. In symptom- and ELISA-based surveys of trees in October 1989 and 1990, pin oak bacterial leaf scorch was found in 11 Kentucky cities and towns ranging from Lexington in the east to Paducah in the west. The disease was also found in two northern red oaks (Q. rubra L.) in Lexington and Owensboro.