PURPOSE: To produce the titled agent exhibiting excellent synergistic effect for the control of bacteria belonging to Rhizopus genus, etc., and useful for preventing the degradation of carpet, activated industrial materials and products, by using a mixture of diiodomethyl p-tolylsulfone and another compound as an active component.

CONSTITUTION: The objective agent contains (A) diiodomethyl p-tolylsulfone of formula I useful as an agent for preventing the degradation of paints, wood, cutting oil, plastics, etc. with mircoorganisms belonging to Aspergillus genus, Penicillium genus, Cladosporium genus, etc. and (B) 2,4,5,6-tetrachloroisophthalonitrile of formula II as active components. 1W9pts. of the former compound is mixed with 9W1pts. of the latter compound, and the mixture is added to various industrial materials and products such as emulsion paint, organic adhesive, etc. An exterminating antiseptic and fungicidal effect can be achieved, and bacteria and fungi belonging to e.g. Aspergillus genus, Penicillium genus, Chaetomium genus, Alternaria genus, Bacillus genus, can be controlled.