Browsing by Subject "Canada thistle"
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Item Biological Control of Canada Thistle in Wetland Prairie Restoration(Minnesota Department of Transportation, 2007-10) Eichstaedt, Kari; Wyse, Donald; Johnson, GreggPseudomonas syringae pv. tagetis (Pst), a phytopathogenic bacterium, was evaluated as natural biological control agent for Canada thistle [Cirsium arvense (L.) Scop.]. Canada thistle patches exhibiting symptoms of Pst infection commonly occur along roadsides in association with perennial grasses and a grass litter layer. Field experiments were conducted to determine if grass and litter provide an environment that supports Pst infection of Canada thistle or if grass, litter, and soil collected from infected Canada thistle patches act as inoculum sources for Pst infection of Canada thistle. This experiment provides evidence that grass and litter are important components of the landscape that support the natural Pst infection of Canada thistle, and perennial grass competition has potential to manage Canada thistle in roadside rights-of-way and wetland restoration sites. A previously published Pst specific primer set was determined to require high Pst populations for detection.Item Controlling Leafy Spurge and Canada Thistle by Competitive Species(1994-06) Biesboer, David D.; Darveaux, Bettina; Koukkari, Willard L.A study was performed to assess the use of perennial native grasses in the control of leafy spurge and Canada thistle and also to evaluate the effects of herbicides applied during the fall to leafy spurge crown buds. As part of an integrated vegetation management program, grass treatments containing the native prairie grass little bluestem established well and were effective at reducing the cover of leafy spurge. Paramount to the success of using native grass species is getting adequate grass establishment which necessitates the careful selection of grass species adapted to the specific site conditions. A fall application of the herbicide picloram at 0.5 and 1.0 lb ai/acre was very effective at controlling leafy spurge and may be mediated via the direct absorption of picloram by the elongated crown buds at this time. The report contains an extensive literature review of the biology and weed control efforts of both leafy spurge and Canada thistle.Item Production and Wind Dispersal of Canada Thistle (Cirsium arvense L.) Achenes(Minnesota Department of Transportation, 2008-09) Becker, R.L.; Haar, M.J.; Kinkaid, B.D.; Klossner, L.D.; Forcella, F.Quantity, quality and dispersal distance of wind-blown achenes and pappi were determined during the peak time of dispersal over twelve site-years in Minnesota during 2006 and 2007. Approximately twice as many pappi than achenes were trapped. Wind blown pappi tend to travel near the ground. Most achenes fell near the parent plants and their population density declined exponentially with increasing distance. Over 80% of pappi collected did not have an achene attached. Concomitantly, seed production in Canada thistle was monitored for 8 site-years in Minnesota. Averaged across years and locations, female Canada thistle shoots that flowered produced an average of 38% empty, 17% shrunken, and 44% normal achenes. Male shoots produce about half the number of seedheads compared to female shoots. A low level of hermaphroditic expression was observed in male shoots. Though seed production by female Canada thistle is extremely variable, when sufficient pollen is available, Canada thistle clearly has the potential to generate significant contributions to seedbanks to maintain invasive stands. However, dispersal by wind is for the most part, local. Long distance dispersal of significant numbers of healthy achenes would be a rare event.Item Radio News Briefs for a Growing Minnesota, May 16, 1969(University of Minnesota, Agricultural Extension Service, 1969-05-16) University of Minnesota, Agricultural Extension Service