The western tarnished plant bug, Lygus hesperus Knight, is an important pest of crops in the western U.S. Research on the biology of L. hesperus often relies on access to healthy insects from laboratory cultures. However, maintenance of colony vigor often requires periodic introductions of field-collected specimens or re-initiation of the colony. Either approach poses a risk of introducing diseases with the field-collected insects. We examined the potential utility of exposure to ultraviolet light (UV-C) as a way to sterilize adult L. hesperus previously treated with spores of Beauveria bassiana (Balsamo) Vuillemin, and also examined the influence of exposure to UV-C on subsequent reproduction by lygus. Mortality of B. bassiana conidia increased rapidly with increased exposure to UV irradiation, which also delayed germination of conidia at exposure times ≥2 minutes. Based on assays 48 hours after exposure to UV, 6.45 minutes of exposure to UV-C (≈130 µW cm^-2) reduced germination of conidia to approximately 1%. When L. hesperus adults treated with B. bassiana were exposed to UV-C for 2 hours, infection by the pathogen was greatly decreased but not eliminated. Similar exposure of untreated L. hesperus adults did not reduce subsequent fecundity. Our results suggest that routine exposure of field-collected adults to UV-C irradiation may reduce the probability of introducing B. bassiana into laboratory colonies with little or no adverse reproductive consequences.