Lecanicillium lecanii is one of entomopathogenic fungus that effective against thrips. The use of the fungus in potato cultivation may increase control threshold of thrips in order to hold environment sustainability. The experiment was aimed to evaluate the control threshold of thrips with add L. lecanii as an biological control agent. The experiment had been conducted in Marga Mekar Village (1,200 m asl.), Pangalengan Sub District, Bandung District, West Java Province. The experiment was arranged in randomized block design with six treatments and each treatment was replicated four times. The treatments tested were (A) control threshold one nymph/leaf + L. lecanii, (B) control threshold six nymphs/leaf + L. lecanii, (C) control threshold 11 nymphs/leaf + L. lecanii, (D) control threshold 16 nymphs/leaf + L. lecanii, (E) insecticide spraying 2x/week, and (F) check, without insecticide and without L. lecanii. Result showed that L. lecanii spraying (1x / week) was able to increase the control threshold of thrips of 10 nymphs/leaf to 16 nymphs/leaf, was able to suppress the use of insecticides by 56.25% to 100%, and was able to suppress the yield loss of potato by 34.98% to 45.74%. Lecanicillum lecanii as a biological control agent of thrips more appropriately used in the dry season, when the disease intensity is low, in order to avoid sistemic fungicide application that able kill the entomopathogenic fungus.