Bioacaricides in Crop Protection—What Is the State of Play?

Growing demands for environmentally safe and sustainable pest management have increased interest in biopesticides as alternatives to synthetic chemical pesticides. This review presents the current status of bioacaricides, defined as commercial biopesticide products based on microorganisms (microbial acaricides) and biologically active substances of microbial, plant or animal origin (biochemicals and semiochemicals) used in crop protection against spider mites (Tetranychidae) and other plant-feeding mites. The most important microbial bioacaricides are mycopesticides, which are products manufactured from living propagules of Beauveria bassiana s.l. and several other acaropathogenic fungi. Products based on avermectins and milbemycins, secondary metabolites of actinomycetes, are well known examples of biochemicals of microbial origin. Among the biochemicals of plant origin, the most widely used to date have been the products based on pyrethrum—obtained from the Dalmatian daisy, Tanacetum cinerariifolium (Asteraceae)—and azadirachtin, obtained from the Indian neem tree, Azadirachta indica (Meliaceae). In recent years, products based on essential oils from aromatic plants belonging to the families Lamiaceae, Myrtaceae, Rutaceae and others have also gained increasing importance in the market. Special emphasis in this review is given to the compatibility of bioacaricides with predatory mites of the family Phytoseiidae as biological control agents used in the integrated management of plant-feeding mites.