Six fungal species were selected from a total of 76 on the basis of their antagonism to the onion white rot pathogen, Sclerotium cepivorum, in dual culture. Gliocladium roseum, G. virens, Trichoderma viride and Coniothyrium minitans exhibited their antagonism by competing successfully with the pathogen for space and nutrients whilst Chaetomium globosum and Penicillium expansum released antibiotic substances into the agar medium which inhibited the growth of S. cepivorum at a distance. Four of the six test fungi were also able to colonise and degrade sclerotia of the pathogen. Gliocladium roseum was tolerant of the dicarboximide fungicides, iprodione, vinclozolin and procymidone. None of the antagonists were pathogenic on onion seedlings in vitro and they therefore show promise for use as biocontrol agents against onion white rot.

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