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 re stricted in Argentina to plants of two genera, Grindelia and Gutierrez ia (Asteraceae: Astereae). Field examination of 51,622 plants of 67 sp ecies of Asteraceae at 286 locations revealed that larvae completed th eir development only in Grindelia chiloensis (Corn.) Cabrera, Grindeli a tehuelches Cabrera, Gutierrezia solbrigii Cabrera, Gutierrezia spath ulata (Phil.) Kurtz., and Gutierrezia mandonii (Sch. Bip.) Solbrig. In multiple-choice tests in the laboratory, using cut stems of 37 specie s in 27 genera and eight tribes of Asteraceae, 93.5% of the neonate la rvae that entered stems entered those of 4 species of Grindelia and Gu tierrezia and 95.7% entered these plus the 1 other species of the subt ribe Solidagininae tested. In no-choice tests using potted plants in t he laboratory garden, neonate larvae placed in holes drilled in the st ems of 28 species of plants developed to the adult stage only in Gr. c hiloensis but reached the fourth instar also in Grindelia pulchella Du n., Gu. solbrigii, and Solidago chilensis Meyen. The no-choice and mul tiple-choice laboratory tests, interpreted through the three basic ele ments 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.