Abstract: Liquid biocidal concentrates which can be diluted into aqueous microemulsions useful for wood preservation, contain (A) at least one triazole fungicide, at least one quaternary ammonium fungicide, and at least one benzimidazole fungicide, and (B) a combination liquid solvent medium therefor, including an ether of an alkanol and of a diol, as well as a carboxylic acid, and, optionally, (C) an additive comprised of oil(s) and/or fixative(s).