Submitted to: International Knapweed Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 1/1/2001
Publication Date: 3/1/2001
Citation: BALCIUNAS, J.K., VILLEGAS, B. CHAETORELLIA SUCCINEA - IS THIS UNINTENTIONALLY RELEASED NATURAL ENEMY OF YELLOW STARTHISTLE SAFE?. INTERNATIONAL KNAPWEED SYMPOSIUM. 2001. p. 94-95. Interpretive Summary:
Technical Abstract: We report our field and laboratory investigations into the host range of Chaetorellia succinea, an unintentionally introduced tephritid fly whose larvae damage the seeds of yellow starthistle. Earlier, in brief investigations in Europe, Ch. succinea had been rejected as a potential agent for yellow starthistle because of concern that it might develop on safflower, Carthamus tinctorius. We planted four varieties of safflower as "trap plants" at several sites where this fly was abundant, and also monitored safflower fields at 47 sites in California. We also collected heads from almost 20 varieties of Cirsium and Centaurea at field sites in California and Oregon. In our laboratory, we exposed Ch. succinea to five varieties of safflower, under both choice and no-choice conditions, and also tested, under no-choice conditions, another 10 species in the thistle tribe. Our lab and field test both conclusively show that there is no risk to native species of Cirsium thistles from Ch. succinea. However, under no-choice conditions, and sometimes even in our choice tests, oviposition and eventual emergence was observed on nearly all of the safflower varieties we tested. Although none of the "trap" safflower we grew at field sites with large populations of this fly showed any damage from this fly, we did eventually detect the presence of Ch. succinea at two of the 47 safflower fields we monitored. This fly is now widespread in California, and has established in at least four other states.