Six cultivars of honeylocust, Gleditsia triacanthos L., were inoculated with the canker fungus Thyronectria austro-americana to test the hypothesis that trees stressed by Thyronectria are rendered more attractive to wood borers, or more suitable as hosts for the bag worm, Thyridopteryx ephemeraeformis (Lepidoptera: Psychidae). Relative susceptibility of cultivars to the fungus, and seasonal flight activity of associated borers were also monitored. Cultivars ‘Sunburst,’ ‘Shademaster,’ and ‘Rubylace’ developed the largest cankers; ‘Imperial’ was variable, and ‘Skyline’ and ‘Trueshade’ were somewhat less susceptible. Adults of four species of Agrilus borers (Coleoptera: Buprestidae) were abundant on honeylocust. Beetles were active from late May until August. Adult borers were attracted equally to infected and non-infected trees, but borers apparently failed to colonize trees of either type. Levels of soluble protein were higher in foliage of diseased trees, but growth and survival of bagworms were similar for both treatments. This study did not support a close relationship between Thyronectria canker disease of honeylocust and predisposition to wood borers, at least on relatively vigorous hosts.
Support for this project was provided by the Horticultural Research Institute, 1250 I Street, N.W., Suite 500, Washington, DC, 20005 and by the International Society of Arboriculture Research Trust. Published as Kentucky Agricultural Experiment Station Journal Article no. 93-7-64. The authors thank C. Jaggie, Ashland Oil, Inc., Lexington, and G. Lewis, Jefferson State Vocational School, Louisville, KY, for their cooperation. We also thank S. Wellso (USDA-ARS, Purdue University) for identifying reference specimens of Buprestidae, and J. Frank Schmidt & Son Co., Boring, OR, for donating trees used in these studies. J. Doney, B. Kennedy, C. Redmond, and P. Spicer (University of Kentucky) provided able technical assistance.
2Professor, University of Kentucky, Department of Entomology, S-225 Agriculture Science Bldg. N., Lexington, KY 40546-0091.
3Extension Professor, University of Kentucky, Department of Plant Pathology, S-305 Agriculture Science Bldg. N., Lexington, KY 40546-0091.