| The primary goal of this dissertation research was to assess the use of compost for the control of several foliar and soil borne diseases commercially important in the Pacific Northwest. The use of compost teas to control of gray mold (Botrytis cinerea) on geraniums, powdery mildew (Podospheara pannosa var. rosae), rust ( Phragmidium spp.), and black spot (Diplocarpon rosae) on field grown roses, and damping-off caused by Pythium ultimum was examined. The goal was to optimize control through manipulation of compost tea production parameters of compost source, fermentation nutrients, fermentation duration, stirring, depth of liquid, aeration, and spray adjuvants.; No one optimal set of compost tea production practices could be determined for control of grey mold, however, empirical evidence indicated that the probability of disease suppression could be increased through compost tea production choices, especially compost source and addition of fermentation nutrients.; Incorporating compost into container media resulted in variable suppression of seedling damping-off across compost sources. Damping-off caused by P. irregulare was suppressed by 66% of the compost samples, P. ultimum by 56% of the samples, and Rhizoctonia solani by 17% of the samples. R. solani damping-off was made worse by 42% of the compost samples. Damping-off of the three pathogens was suppressed by 11% of the compost samples. Twenty-two percent of the samples did not significantly suppress damping-off disease caused by any pathogen.; Manipulating compost production to consistently attain P. ultimum damping-off suppression was investigated. By placing hot compost removed from curing piles into sterile storage, it became clear that compost required recolonization by exogenous mesophyllic microflora for the rapid development of Pythium damping-off.; Compost can be used to assist in plant disease management resulting in significant disease control. However, as with most biological methods, inconsistency is still an issue. Research on application methodology and further refinement of composting and compost tea production practices (i.e. compost source and spray adjuvants) will likely increase the potential for consistently suppressing plant disease with these technologies. |
