Characterization and assessment of compost for suppression of selected turfgrass diseases
The use of composts for turfgrass disease management allows for a reduction of pesticide use in traditional chemical control practices. Up to five composts were characterized and evaluated for suppression of turfgrass diseases. The monitoring of temperature and oxygen throughout the composting process was the best method tested in evaluating compost maturity. Controlled environment experiments with selected compost treatments suppressed dollar spot of turf ('Sclerotinia homoeocarpa' F. T. Bennett) by up to 58% and, in field trials, were not significantly different than fungicide controls ('P' = 0.05). Similarly, fall applications of compost reduced snow mould ('Microdochium nivale' Fr. Samuels and Hallet, ' Typhula ishikariensis' Lasch ex. Fr.) severity to levels not significantly different from fungicide controls and increased green-up of turf (recovery from disease and/or winter dormancy) by up to 63% compared to fungicide and 54% compared to fertilizer controls ('P' = 0.05). Microbial characterization of composts revealed high culturable colony counts. Moreover, 29% of bacteria isolated displayed proteolytic activity. Two bacterial identification systems gave variable results, whereas phospholipid fatty acid (PLFA) analysis was a valuable indicator of microbial community dynamics. Many bacterial isolates tested in the plate challenge experiment displayed antagonistic activity towards selected turfgrass pathogens. Antagonistic activity of composts relies on a number of factors, and although their relative importance varies, microbial activity levels, population dynamics, nutrient aspects, as well as other associated chemical and physical factors all have a part in turfgrass disease suppression.