Laboratory and production bed observations reveal that the major fungal competitors of the Chinese straw mushroom growing on sugarcane bagasse are Sclerotium rolfsii Sacc., Corticium sp., Coprinus sp., Aspergillus flavus Link ex Fries and Chaetomium globosum Kunze ex Steud. Because of their perceived importance, these five fungi were selected for control studies. The selectivity of fungicides for the control of these fungi in Chinese straw mushroom beds was tested in vitro. Benomyl, captan, carboxin, chloroneb, mancozeb and penthachloronitrobenzene (PCNB) were tested in poison agar tests at the rates of 1, 10 and 100 p/m a.i. with Chinese straw mushroom and the selective competitors. Mushroom radial growth was reduced in all treatments of carboxin and at 10 and 100 p/m of chloroneb. Compared to these, PCNB was intermediately toxic. Chinese straw mushroom was tolerant to all concentrations of benomyl, captan and mancozeb. A. flavus radial growth was highly reduced with benomyl and slightly reduced by carboxin, chloroneb and PCNB. S. rolfsii showed growth reduction at 10 and 100 p/m of PCNB, chloroneb and carboxin. Growth of Coprinus sp., Corticium sp., C. globosum and A. flavus was reduced over 90% with treatments of benomyl at 100 p/m. Fungicidal sprays were evaluated in vivo on sugarcane bagasse and coffee pulp beds. Poor pasteurization of the coffee pulp was associated with rampant development of Aspergillus fumigatus Fries. and Mucor sp. Partial superficial control of these fungi was obtained with mancozeb alone (50 to 75% reduction of visible growth). Benomyl alone and in combination with mancozeb gave excellent suppression of fungi on the mushroom beds (90% reduction of visible growth). None of the treatments controlled fungi within the beds.