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Abstract: Diehhomyces microsporus (Diehl & Lamb ) Gil , commonly known as Calves' brains fungus, is one of the most important pathogens in mushroom beds under the cultivation conditions in Taiwan. It invades the bed areas and acts as a serious competitor with mushroom. Infested mushroom beds may eventually cease to produce fruit-bodies Ascospores of the fungus survive heating at 82°C for a period up to five hours and are resistant to several fungicides in common use (Gandy et al., 1953; Kligman, 1944). Gandy et al. (1953) suggested the treatment of compost with 0.1% copper sulfate to control the fungus but growers found the method unsatisfactory, giving inconsistent results when used in commercial houses. Kligmann (1944) mentioned as a control measure the running of the spawn at a temperature of 15°C (60°F) at which the ascospores of Calves' brains fungus do not germinate. However, difficulties may arise in warm weather when temperature control is not provided. The value of antagonistic microorganisms m the control of plant diseases has long been recognized (Baker, 1968; Boosahs and Mankau, 1965; Cooper and Chilton, 1950; Kelner, 1948; Tsao et al., 1960). Antagonists are of particular value in combating diseases caused by soilinhabiting pathogens (Baker, 1968; Gregory et al., 1952; Huber et al., 1966; Lockwood, 1964). Effectiveness can be greatly enhanced by the presence of a compound which selectively favors the antagonists (Baker, 1968; Lockwood, 1964) or by the addition of a large quantity of organic substances to the soil (Boosalis, 1956; Lockwood, 1964). The first system utilizes chemicals and procedures which may at times create the problem of chemical residues. The latter system evidently suits the purpose of disease control in mushroom beds in which a high organic content exists. Actinomycetes have been shown to propagate rapidly during fermentation of compost and are beneficial to the mushroom (Kligman, 1950). Blondeau (1950) isolated thermophhic actinomycetes and identified them as to belonging to Streptomyces and Micromonospora. Waksman (1950) also noted that many species of actinomycetes in soil or compost have an antibiotic activity to fungi. Recently, antibiotic substances secreted by actinomycetes were shown to inhibit the germination of ascospores and the growth of mycelium of Calves' brains fungus (Lin, 1971). In this study, attempts are made to search for antagonistic microorganisms to the Calves' brains fungus and to evaluate them for their value as possible biological control agents. A greater emphasis is given to the actinomycetes.
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