The entomopathogenic fungus, Beauveria bassiana (Balsamo) Vuillemin, has a high potential to control the populations of the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), a significant pest of strawberries. B. bassiana isolates INRS-IP and INRS-CFL were highly infective against L. lineolaris populations under laboratory conditions. LC₅₀ values were of  7.8x10⁵ and 5.3x10⁵ conidia/ml respectively for INRS-IP and INRS-CFL, and LT₅₀ values were respectively of 4.46 and 4.37 days at a concentration of 1x10⁷ conidia/ml. In strawberry field conditions, insecticide efficacy of the B. bassiana isolates was investigated by monitoring variations in L. lineolaris nymph populations’ densities. Using a randomized block design with four replicates, multiple applications of B. bassiana isolates INRS-IP and INRS-CFL were applied at rates of 1x10¹¹ and 1x10¹³  conidia/ha weekly during four weeks. The multiple sprays of B. bassiana triggered in a significant reduction in L. lineolaris nymph populations on strawberry plants. These results suggested that isolates INRS-IP and INRS-CFL of B. bassiana are an effective tool for the control of L. lineolaris nymph populations in strawberry field. During the field experiment, persistence of insecticide activity and viability of B. bassiana conidia were also monitored. To assess the persistence of conidial insecticide activity, the pathogenicity test was carried out in laboratory on L. lineolaris adults exposed to treated leaves collected every 3 days. After treatments, the viability of B. bassiana conidia on foliage was also investigated by measuring the number of colony forming units (CFUs) recovered from strawberry leaves collected every 3 days. Field evaluation of B. bassiana isolates INRS-IP and INRS-CFL efficacy against L. lineolaris populations revealed the presence of viable and infective conidia up to 6 days on strawberry foliage after application. This study is the first to highlight that multiple treatments must be taken into account in foliar application of B. bassiana conidia in strawberry crops to control L. lineolaris populations.