A multifunctional broad spectrum antimicrobial composition is described. The composition can be incorporated into a wood preservative, or used as an additive to provide antimicrobial properties to water-based wood coatings. The composition is a concentrated water-miscible emulsion containing 3-iodo-2-propynyl N-butylcarbamate (IPBC), carbendazim (BCM) and propiconazole (PPCZ), and has antimicrobial activity against a wide variety of fungal organisms, including surface molds, blue stain fungi and wood rotting fungi. The composition is useful for antimicrobial protection of wood substrates such as green lumber, engineered wood, and wood composite products.
