Host Range of the Argentine Root Borer Carmenta haematica (Ureta) (Lepidoptera: Sesiidae), a Potential Biocontrol Agent for Snakeweeds ( Gutierrezia spp) in the United States

The Argentine root-boring sesiid moth Carmenta haematica (Ureta) is restricted in Argentina to plants of two genera, Grindelia and Gutierrezia (Asteraceae: Astereae). Field examination of 51,622 plants of 67 species of Asteraceae at 286 locations revealed that larvae completed their development only in Grindelia chiloensis (Corn.) Cabrera, Grindelia tehuelches Cabrera, Gutierrezia solbrigii Cabrera, Gutierrezia spathulata (Phil.) Kurtz., and Gutierrezia mandonii (Sch. Bip.) Solbrig. In multiple-choice tests in the laboratory, using cut stems of 37 species in 27 genera and eight tribes of Asteraceae, 93.5% of the neonate larvae that entered stems entered those of 4 species of Grindelia and Gutierrezia and 95.7% entered these plus the 1 other species of the subtribe Solidagininae tested. In no-choice tests using potted plants in the laboratory garden, neonate larvae placed in holes drilled in the stems of 28 species of plants developed to the adult stage only in Gr. chiloensis but reached the fourth instar also in Grindelia pulchella Dun., Gu. solbrigii, and Solidago chilensis Meyen. The no-choice and multiple-choice laboratory tests, interpreted through the three basic elements of host specificity of insects, support the host range observed in the field. C. haematica is the most specific insect yet tested for biological control of snakeweed. It is sufficiently host specific for introduction into quarantine in the United States for further testing and possible future release in the field.