This invention relates to synergistic microbicidal combinations of: 1) (A1) 2-methyl-4-isothiazolin-3-one with (B1): one or more compounds selected from the group consisting of anisic acid, decylene glycol, diethylene triamine pentacetic acid (DTPA), hydroxyethyl ethylenediamine triacetic acid (HEDTA), imminodisuceinate (IDS), maleic acid, methyl glycine diacetic acid (MDGA), phenoxypropanol, phytic acid, and propionic acid. 2) (A2) 1,2-benzisothiazolin-3-one with (B2): one or more compounds selected from the group consisting of anisic acid, capric acid, decytene glycol, diethylene triamine pentacetic acid (DTPA), etidronic acid, gluconic acid, hydroxyethyl ethylenediamine triacetic acid (HEDTA), imminodisuccinate (IDS), maleic acid, methyl glycine diacetic acid (MDGA), phenoxypropanol, phytic acid, and propionic acid. The examples show that abovementioned combinations have greater efficacy than would be expected from combinations of the individual components against one or more of following microorganisms: E. coli, C. albicans and A. niger.
