Seasonal dynamics of Urophora quadrifasciata on spotted knapweed in the Arkansas Ozarks

Abstract

Periodic sweep-net sampling and capitula sampling were conducted between April and October 2007 to determine the seasonal phenology of Urophora quadrifasciata (Meigen) (Diptera: Tephritidae) on spotted knapweed, Centaurea stoebe subsp. micranthos (Gugler) Hayek (Asteraceae), in the Arkansas Ozarks of the United States of America. Urophora quadrifasciata produces up to three generations in Arkansas, rather than being bivoltine as in the northern United States of America. The first, second, and third generations of U. quadrifasciata reached peak adult numbers around 26 May, 29 June, and 27 July, respectively. Males tended to emerge earlier than females but the female:male ratio was approximately 1:1 for most of the season. The majority of the offspring of the three generations emerged between June and October, while approximately 38% entered diapause and emerged as adults in April-June of the following year; 3.4 ± 0.1 (mean ± SE) (range 1–12) flies emerged from each infested capitulum. The absence of other, competing knapweed biological control agents as well as very low rates of parasitism, mild weather conditions, and a longer knapweed growing season likely contributed to the adaptation and establishment of U. quadrifasciata on spotted knapweed in Arkansas.

Biocontrol without borders: the unintended spread of introduced weed biological control agents

“…Recently, the houndstongue root weevil Mogulones cruciger Herbst, which was released in Canada in 1997, has dispersed south across the US border where it may feed on native Boraginaceae (Andreas et al 2008). Similarly, the seed head fly Urophora quadrifasciata (Meigen) was introduced into Canada in the early 1970s but spread across the USA border and can now be found in much of North America, including the states of Arizona and Arkansas (Story 1985;Duguma et al 2009). In contrast, the eriophyid mite Eriophyes chondrillae (Canestrini) and the rust fungus Puccinia chondrillina Bubak and Sydow were released for control of Chondrilla juncea L. in the western USA but spread north to British Colombia, Canada (Julien and Griffiths 1998).…”

Biological control of invasive plant species: a reassessment for theAnthropocene

“…An example is the picture‐winged flies ( Urophora spp., Tephritidae) released against knapweeds. When attacking a target species, these species show a single generation in colder regions, but can have up to four generations in warm temperate zones (Duguma et al ., ). As growing seasons expand, at least some portion of the biological control agents will be able to exploit this increase by increasing the number of generations produced per growing season.…”

Larinus minutus(Coleoptera: Curculionidae), A Biological Control Agent of Spotted Knapweed (Centaurea stoebessp.Micranthos), Established in Northern Arkansas

“…This seedhead galling fly was introduced from Russia into Canada in 1980 and has since been redistributed or spread on its own to several states in the northeastern and northwestern United States (Story 2002). Duguma (2008) found that U. quadrifasciata reduced the number of seeds produced by spotted knapweed by 44% late in the season (Aug), at a time when plants are more environmentally stressed. However, the fly did not significantly reduce the number of seeds produced earlier in the season, a time when knapweed is most robust (Duguma 2008).…”