Abstract: The invention relates to acaricidal compositions containing as active ingredient: the fermentation broth or cell-free fermentation broth, of a concentrate of the fermentation broth or cell-free fermentation broth, or a solidified form of the fermentation broth or cell-free fermentation broth of one or two bacterium strains deposited at the National Collection of Agricultural and Industrial Microorganisms, Budapest, Hungary under the identification Nos. 001083 and 001086 or of their mixed micropopulation, if desired, in a sterilized state, optionally together with the metabolism products arising during the fermentation and inutilized nutriments, as well as one or more solid and/or liquid carrier(s) (preferably sugar or a grist of natural minerals), or an inert solvent (e.g. water) and, if desired, with surface active (preferably anionic or nonionic emulsifying or dispersing) agents.