In California, Asian citrus psyllid vectors the bacterium Candidatus Liberibacter asiaticus, which causes the lethal citrus disease huanglongbing. The top priority for California's citrus industry has been to diminish the rate of bacterium spread by reducing Asian citrus psyllid populations in urban areas, where this pest primarily resides. Attempts at eradicating and containing the psyllid with insecticides were unsuccessful. An alternative approach has been a classical biological control program using two parasitoids from Pakistan, Tamarixia radiata and Diaphorencyrtus aligarhensis, which attack the psyllid nymphs. T. radiata has established widely and, in combination with generalist predators, natural enemies are providing substantial control of psyllids in urban areas.