Phytophagous Insects That Attack Larrea spp. (Zygophyllaceae) in Argentina and Their Potential for Biocontrol of Creosotebush (L. Tridentata) in North America

The genus Larrea originated in semiarid southern South America, where four species occur today. It spread to semiarid southwestern North America only 11,000 to 14,000 years before present where one species, L. tridentata (DC.) Coville (creosotebush), evolved. Creosotebush has increased greatly during the past 100 years to become a weed of major importance in rangelands by competing with beneficial forage plants. Biological control is possible through the introduction of natural enemies from closely related species of Larrea in Argentina. We and other workers have found a total of 110 species of insects that attack Larrea spp. there. Probably 15 species were sufficiently damaging, consistently found, and apparently host specific in our field collections to warrant further testing as candidates for introduction. These include three species of grasshoppers, three scale insects, two flat-headed wood-boring beetles, one leaf chafer, two jumping plant lice, several undetermined species of foliage-feeding caterpillars, darkling beetles, and a katydid.