Attack of Urophora quadrifasciata (Meig.) (Diiptera : Tephritidae) a biological control agent for spotted knapweed (Centaurea maculosa lamarck) and diffuse knapweed (C. diffusa lamarck) (Asteraceae) by a parasitoid, Pteromalus sp (Hymenoptera : Ptero

摘要

Urophora quadrifasciata (Meig.) a seedhead fly released in North America for biological control of Centaurea maculosa and C. diffusa is parasitized by a Pteromalus sp. Parasitism up to 60% of U. quadrifasciata was found in samples of seed heads of C. maculosa and C. diffusa collected from 54 of the 59 counties sampled in Michigan and in one sample of C. maculosa seed heads from Hennepin County, Minnesota. Parasitism of U. quadrifasciata has rarely been reported.