Home on the Range: Establishment of a Canada Thistle Biocontrol Agent

Predatory and Parasitic Insects Associated with Urophora cardui L. (Diptera: Tephritidae) Galls on Canada Thistle, Cirsium arvense L. (Asterales, Asteraceae) in North Dakota

“…We sampled U. cardui galls on Canada thistle in 2012 and 2013 from field sites in the eastern and western parts of North Dakota, U.S. ( Table 1 ). These sites were part of a state-wide Canada thistle biological control project, where in 2004, the North Dakota State Department of Agriculture released adult stem-mining weevils, Hadroplontus ( Ceutorhynchus ) litura Fabricius (Coleoptera: Curculionidae) (see Prischmann-Voldseth et al [ 22 , 23 ] for details). In 2009, we established permanent transects at each site to enable the systematic collection of samples, with three 15.9 m-long transects extending out from the original weevil release site at the linear edge of the thistle patch, which was created by anthropogenic activity (e.g., a road or field edge), creating four inter-transect spaces [ 22 ].…”

“…These sites were part of a statewide Canada thistle biological control project, where in 2004, the North Dakota State Department of Agriculture released adult stem-mining weevils, Hadroplontus (Ceutorhynchus) litura Fabricius (Coleoptera: Curculionidae) (see Prischmann-Voldseth et al [22,23] for details). In 2009, we established permanent transects at each site to enable the systematic collection of samples, with three 15.9 m-long transects extending out from the original weevil release site at the linear edge of the thistle patch, which was created by anthropogenic activity (e.g., a road or field edge), creating four inter-transect spaces [22]. In 2012, we collected U. cardui galls from May 2 to May 10, prior to the emergence of adult flies, in two to four of the inter-transect areas at each site (i.e., replicate) listed in Table 1.…”

“…Little is known about the insect species that occur within U. cardui galls in North Dakota, a north-central U.S. state, although the parasitoid community from nearby states has been studied [ 10 ]. Therefore, while monitoring the field releases of Canada thistle biocontrol agents [ 22 , 23 ], we collected additional U. cardui galls from Canada thistle in order to quantify the identity and density of insects associated with U. cardui galls and examine the relationships between gall size and insect density and biomass. We also provide the first report of a previously unknown predaceous beetle within the thistle galls, Isohydnocera tabida (LeConte) (Coleoptera: Cleridae).…”