PROC. ENTOMOL. SOC. WASH. 92(3), 1990, pp. 426-430 HOST SPECIFICITY OF CHAETORELLIA AUSTRALIS (DIPTERA: TEPHRITIDAE) FOR BIOLOGICAL CONTROL OF YELLOW STARTHISTLE {CENTAUREA SOLSTITIALIS, ASTERACEAE) D. M. Maddox,' a. Mayheld,' and C. E. Turner-Biological Control of Weeds, U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, California 94710. Abstract.— The flower head tephritid fly Chaetorellia australis Hering was studied to determine its host specificity for biological control of Centaurea solstitialis L. (yellow starthistle) in the United States. Flies from flower heads of C. cyanus L. collected in northern Greece were tested for oviposition and development on nine plant species in no-choice host tests during the summers of 1986-87 in Albany, California. Oviposition and development occurred on only two species: flies damaged 93.7% (1986) and 79.6% (1987) of the heads of C. solstitialis and 85.8% of the heads of C. cyanus. No evidence of oviposition and development occurred on the other test plant species: Centaurea amer-icana Nutt., Centaurea rothrockii Greenm., Carthamus tinctorius L., Cirsium occidentale (Nutt.) Jeps., Helianthus annuus L., Zinnia elegans Jacq., and Lactuca sativa L.. More than 92% of the pupal fly-yielding flower heads produced only one pupal fly, while less than 8% of these flower heads had two pupal flies, indicating that the fly is not particularly gregarious. Key Words: biological control, weed, rangeland, insect Yellow starthistle (Centaurea solstitialis ingspeciesthat is especially invasive on dis-L., Asteraceae) is a wmter annual that is a turbed lands. Its primary economic impact naturalized weed primarily in the western is on rangelands where it reduces livestock United States. Surveys indicate that it oc-productivity because of its unpalatability, curs in 208 counties in 23 states within the competitiveness, and toxicity to horses U.S. (Maddox et al. 1985), and infestations (Maddox et al. 1985). Yellow starthistle is in California alone have reached an esti-believed to be native to the eastern Medi-mated 3.25 million gross hectares (Maddox terranean Basin and western Asia (Prodan and Mayfield 1985). The weed is a pioneer-1930). Multiple introductions have proba-bly occurred in the U.S. (Maddox and May-field 1985). An analysis of seeds contained ' D. M. Maddox is a Research Entomologist (retired) in adobe bricks from early buildings in Cal-and A. Mayfield is a Biological Technician (retired). ifomia indicates that yellow Starthistle was Current addresses ofD.M.M. and A.M.: 18469 Chap-introduced in the nineteenth century after arralDr..Penn Valley, CA 95946 and 548 1 Crittenden ,_.. ^,j , ,„., ,, , j n n St.. Oakland, CA 94601 respectively. 1824 (Hendry 1931, Hendry and Bellue = Please direct all requests for repnnts to C. E. Turn-1936, Maddox and Mayfield 1985). er. A search for natural enemies of yellow
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