ESTABLISHMENT AND DISPERSAL OF UROPHORA-AFFINIS (DIPTERA, TEPHRITIDAE) AND METZNERIA-PAUCIPUNCTELLA (LEPIDOPTERA, GELECHIIDAE) IN SOUTHWESTERN VIRGINIA

Two European gall-producing insects, Urophora affinis Frfld. (Diptera: Tephritidae) and Metzneria paucipunctella (Zeller) (Lepidoptera: Gele chiidae) were introduced into Virginia in 1986 for biological control of spotted knapweed (Centaurea maculosa Lam.). Adults of U. affinis (n = 2625) and M. paucipunctella (n = 450) were released at two sites in Montgomery County, Virginia, and their populations were monitored yea rly by dissecting spotted knapweed flower heads. Beginning in 1992, kn apweed samples collected at various distances from the release sites w ere checked for dispersal. U. affinis is well established and is sprea ding slowly. The number of larvae per flower head and the seed numbers are inversely related as plants with the greatest number of larvae pe r spotted knapweed head had the lowest number of seeds. Knapweed densi ty has declined at one of the release sites which had the highest rate of infestation by U. affinis. Establishment of the moth, ICI. paucipu nctella, is less certain as it has been recovered at a very low level from only one site. (C) 1996 Academic Press, Inc.