2018 ASHS Annual Conference

Interspecific hybrid impatiens have been recently identified as a host for the soil-borne fungal pathogen Macrophomina phaseolina. No control methods for this fungus have been developed in impatiens for growers, landscapers, or homeowners. The goal of this study was to screen the efficacy of three commercially available fungicides (Tanos, Banrot, and T-Bird) on biomass accumulation of M. phaseolina (isolate MP1) in vitro. To accomplish this, M. phaseolina was grown in liquid basal media containing one of the three fungicides at 0.25x, 0.5x, 1.0x, or 2.0x the recommended application rate in a completely randomized design. All samples were grown at 27°C and shaken continually to keep the fungicide suspended and the media oxygenated. Biomass accumulation was quantified using dry weights of the samples taken at three sampling dates. Banrot applied at 2.0x concentration and T-Bird applied at 1.0x concentration were the most effective at reducing dry weights of M. phaseolina by more than 25%. The greatest reduction (31.7%) was achieved by T-Bird at 1.0x concentration. M. phaseolina treated with Tanos 0.25x were 12.5% larger than the controls after 3 weeks; however, it was able to limit growth at the 2.0x concentration. Future work will include field trials to determine the efficacy of Banrot and T-Bird in situ. This will include identifying the optimal rates and application time to control the pathogen.