BIOLOGICAL AND INTEGRATED CONTROL OF FUSARIUM BASAL ROT OF NARCISSUS USING MINIMEDUSA-POLYSPORA AND OTHER MICROORGANISMS

In laboratory experiments several soil‐ and bulb‐borne micro‐organisms exhibited antagonism towards Fusarium oxysporum f.sp. narcissi. One‐third of these micro‐organisms were also found to be tolerant to thiabendazole, a fungicide commonly used for the control of this pathogen. Micro‐organisms showing high levels of in vitro antagonism and/or tolerance to thiabendazole were screened in pots of natural soil artificially infested with the pathogen. Six of the micro‐organisms were found significantly to suppress basal rot development when used as pre‐planting bulb treatments. Minimedusa polyspora and a Streptomyces species were most effective, giving disease levels 55.72% and 56.88% lower than the control. In a 1‐year field trial pre‐planting bulb treatments with M polyspora, a Streptomyces species and an isolate of Trichoderma viride significantly suppressed reductions in flower numbers, reductions in bulb yield, and percentage infection. The integration of T. viride with thiabendazole gave bulb yields significantly greater than either T. viride or thiabendazole alone whilst the integration of M. polyspora and thiabendazole resulted in significantly greater flower numbers and significantly fewer bulb infections than either treatment alone. Copyright © 1990, Wiley Blackwell. All rights reserved