Andean potato weevils (Premnotrypes spp.) are the most important insect pests of potatoes throughout the Andean region. Despite being endemic to the Andes, no significant natural enemies of these pests have been reported until recently. A natural enemy, an undescribed entomopathogenic nematode from the genus Heterorhabditis designated Alcázar-1, was isolated from potato weevils in a potato storage unit in Peru. Our objective was to characterize the potential of this nematode to suppress Premnotrypes suturicallus populations. We evaluated the tolerance of this nematode to the cold Andean temperatures, its infectivity against different stages of P. suturicallus, and its recycling potential within this host. Heterorhabditis sp. Alcázar-1 was infectious to Galleria mellonella larvae at temperatures (mean 11.1 °C; range 8.6-14 °C) similar to those recorded for daily fluctuations in the Andes. In laboratory bioassays, the nematode protected potato tubers from infestations by neonate P. suturicallus larvae and killed weevil larvae within the tubers before significant damage was incurred. Median lethal concentration (LC50) for P. suturicallus pre-pupae was 5.9 infective juveniles/host reflecting high susceptibility. At this concentration, mortality increased over a 7-day period, resulting in 66% pre-pupae, 65% pupae and 52% teneral adults killed by the nematode. Alcázar-1 has a high reproductive potential in P. suturicallus pre-pupae, producing an average of 97,817 infective juveniles per host. These results suggest that Alcázar-1 has excellent potential for biological control of the Andean potato weevil. © 2006 Elsevier Inc. All rights reserved.