An attempt was made to develop an ecosystems approach for the control of the nuisance aquatic plant-Eurasian milfoil, Myriophyllum spicatum L. To this end a cellulolytic fungus, Mycoleptodiscus terrestris (Gerdemann) Ostazeski (M.t.), and a pectinolytic bacterium, Bacillus sp. strain P8 (BSP8), were isolated from the microbial populations naturally resident in the phyllosphere of this plant. These organisms grew compatibly with each other, were able to compete successfully with other microflora on the plant surface and were able to resist the inhibitory action of phenolic compounds produced by the plant. Application of these organisms to the plant, after growth in appropriate media, resulted in plant decline and eventual death. The process of decline included hormone-like stress effects on the plant induced by BSP8 (internodal elongation), increase in strongly pectinolytic microbial populations associated with the plant and penetration into plant tissue by the fungal mycelium. These results were confirmed in a sequence of experiments of increasing volume, conducted in jar, pool and, ultimately, a lake setting. The most rapid decline of the plant, subsequent to inoculation, was observed in jars in the laboratory where high concentration of inoculum and isolation from environmental effects could be maintained. In the pool setting, though the application of M.t. and BSP8 together induced the most significant decline, limits in pool depth and light penetration may also have influenced plant decomposition. Field applications, however, ultimately resulted in the virtual elimination of M. spicatum from a treated plot within 10 weeks. Total numbers of microorganisms isolated from M. spicatum tissues were generally 2-4 orders of magnitude higher than numbers obtained from the adjacent water profile, reflecting the substrate commitment of the microorganisms to the plant. The numbers of organisms were greater on treated than untreated tissues and parallel increases were observed in the water profile. These results were confirmed by observation under the scanning electron microscope. Specificity trials of M.t. infectivity revealed it to be very weakly pathogenic to several aquatic species and terrestrial plants and thereby without potential significant impact outside the area of designated application.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-7417 |
| Date | 01 January 1987 |
| Creators | Limpa-amara, Yuthana |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
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