Abstract: Beauveria bassiana (Balsamo) Vuill. is an entomopathogenic fungus used incontrolling various pests. Previous research showed that B. bassiana, applied to the plant canopy,could exert a significant control of thrips populations, in particular of Frankliniella occidentalisPergande. However, some stages (e.g., prepupae and pupae) of this species develop in the soilbeing less affected by control treatments applied to the canopy. The identification of biologicalcontrol agents active against soil-dwelling stages of F. occidentalis is an important issue for theimplementation of IPM. Here we present laboratory and greenhouse experiments carried out toevaluate the potential of B. bassiana (JW-1 ATCC 74040) in controlling soil-dwelling stages ofF. occidentalis. In laboratory bioassays B. bassiana reduced significantly the emergence ofF. occidentalis adults. In the greenhouse experiment, a significant control of thrips populationwas obtained on cyclamen potted plants.