Bacterial Species Associated with Wetwood of Elm

To investigate the etiology of bacterial wetwood in elm (Ulmus americana), we isolated microflora from wetwood capillary liquid, wetwood, and unaffected sapwood of branches, trunks, and roots. Stem and branch isolation samples were obtained from 52 elm trees, 35- 85 cm in diameter at 1.3 m above mean ground level, and from the roots of 10 trees 42- 78 cm in diameter at 1.3 m stem height. Enrichment broth culturing for 48- 96 hr under aerobic and anaerobic conditions, followed by repeated streaking on agar plates, was used to obtain pure cultures. Fourteen species of bacteria and two species of yeasts were isolated. Enterobacter and Klebsiella species were most often isolated from wetwood tissues. They occurred in greater numbers than Pseudomonas and Bacillus species which were most frequent in unaffected sapwood. The data show that an association of bacterial species produce the complex of symptoms observed.