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Environmental effects on bacterial strains applied to the turfgrass phylloplane
Abstract
Biological controls are needed as alternatives to fungicides for turfgrass disease management. Bacterial strains isolated from grass foliage were tested for inhibition of brown patch disease, caused by Rhizoctonia solani Kühn, on detached blades and potted seedlings of tall fescue (Festuca aurundinacea Schreb. cv. Kentucky 31). Stenotrophomonas maltophilia strain C3 was found to be the most antagonistic in both assays. When strain C3 was applied to field plots of tall fescue, the severity of brown patch disease was not greatly reduced. Effective control of brown patch disease under field conditions by strain C3 is limited by insufficient colonization. Population levels of strain C3 detected under field conditions were over 10 fold lower than the number associated with effective antagonism under laboratory conditions. The influence of irrigation and shading were studied in attempts to improve colonization by strain C3 which was compared with Bacillus megaterium strain B153-2-2 and Enterobacter cloacae strain EcCT-501. To investigate the effects of irrigation timing and frequency on population level of applied bacteria and on the microclimate, three irrigation regimes were tested. Irrigation was applied every morning (daily AM), every evening (daily PM), and every third day in the morning (3-day AM) to perennial ryegrass (Lolium perenne L.). Irrigation regimes had little effect on population levels of applied bacteria, and any observed effect was not consistent across bacterial species. Individual irrigation events were found to remove bacteria in some instances, but all reductions in population numbers were less than 0.5 log CFU/g foliage. Leaf wetness duration tended to be shortest in the daily AM irrigation regime and longest in the 3-day AM irrigation regime. Across all irrigation regimes leaf wetness durations were longer in the lower portion of the canopy than the upper portion of the canopy. The effects of shading on bacterial colonization and environmental parameters were evaluated by suspending shade cloth over tall fescue turf plots in full sun areas. Bacterial colonization of foliage was found to be higher in shaded canopies than in full sun areas. Shading increased leaf wetness duration and relative humidity levels, and decreased the mean and range of canopy air and foliage temperature. It is concluded that the irrigation regimes tested had no deleterious affects on bacterial colonization and appeared to be very compatible with biological control agents. Shaded conditions, in which disease activity would be higher, resulted in a proliferation of biological control agents.
Subject Area
Plant pathology|Ecology|Microbiology|Environmental science
Recommended Citation
Giesler, Loren Joseph, "Environmental effects on bacterial strains applied to the turfgrass phylloplane" (1998). ETD collection for University of Nebraska-Lincoln. AAI9917829.
https://digitalcommons.unl.edu/dissertations/AAI9917829