Effects of Girdling by the Threecornered Alfalfa Hopper on Symptom Expression of Soybean Stem Canker and Associated Soybean Yields. J. S. Russin, Department of Entomology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803-1710. D. J. Boethel, Department of Entomology, and G. T. Berggren and J. P. Snow, Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803-1710. Plant Dis. 70:759-761. Accepted for publication 6 March 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-759.

Soybean (Glycine max) stems with and without basal stem girdles induced by the threecornered alfalfa hopper (Spissistilus festinus) were inoculated artificially at upper (internode 10) and lower (internode 2) sites with the stem canker fungus (Diaporthe phaseolorum var. caulivora). Lengths of resultant cankers were significantly greater on girdled stems than on nongirdled stems. Canker lengths also were greater at upper sites than at lower sites regardless of girdle status of stems. Yields of seed from individual plants were consistently lowest for stems that were both girdled and cankered.