Laboratory and realized host ranges of Chaetorellia succinea (diptera:tephritidae), an unintentionally introduced natural enemy of yellow starthistle

Authors: Balciunas, Joseph; VILLEGAS, BALDO - CDFA, SACRAMENTO, CA

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2007
Publication Date: 8/1/2007
Citation: Balciunas, J.K., Villegas, B. 2007. Laboratory and realized host ranges of Chaetorellia succinea (diptera:tephritidae), an unintentionally introduced natural enemy of yellow starthistle. Environmental Entomology. 36(4):849-857.

Interpretive Summary: In mid-1996, we detected an unintentionally introduced seed-head fly Chaetorellia succinea (Costa) destroying seeds of yellow starthistle, Centaurea solstitialis L., one of the worst weeds in the western United States. Of the 13 relatives of yellow starthistle that we tested in the laboratory, we detected oviposition and development by Ch. succinea on only ythree species of Centaurea: Cnt. americana (American basketflower), Cnt. melitensis (Malta starthistle), and Cnt. sulphurea (Sicilian starthistle). Our field collections and rearing of herbivores from 25 species of plants in the tribe Cardueae, confirmed that the realized host range of Ch. succinea was similar to that predicted from our laboratory investigations. In the field, we found this fly only on Cnt. melitensis, and colleagues have reported this fly from Cnt. sulphurea, both of which are introduced weeds. Centaurea americana is native to 13 states. While Ch. succinea has snot yet been recorded from any of these states, we are concerned that although yellow starthistle is uncommon in most of the states, Ch. succinea may use Cnt. melitensis as a "stepping stone" host to reach Cnt. americana populations in the southwest.

Technical Abstract: Yellow starthistle is one of the most widespread and damaging weeds in western United States. A half dozen overseas insects have been approved for release in the United States as biocontrol agents for this weed, and five of these have become established. During 1996, we discovered yet another insect attacking yellow starthistle heads, the seedhead fly Chaetorellia succinea. Since this fly is now widespread throughout California, we immediately began field and laboratory evaluations of this fly's preference for various plants related to yellow starthistle. After 6 years of testing, we conclude that although this fly will not attack native thistles in the genus Cirsium, but will occasionally oviposit and develop on a few Centaurea species. Although nearly all of the three dozen species of Centaurea in the United States are introduced from overseas, and are considered weeds, two are native, and one of these, American basketflower (Cnt. americana) appears susceptible to attack by this fly. This fly has not yet been recorded from any of the 13 states from which American basket flower has been found. However, we recommend monitoring these plants and other yellow starthistle relatives in Texas and Arizona for possible attack by this fly.