EC02-171 Canada Thistle

Canada thistle [Cirsium arvense (L) Scop.] is one of the seven species defined by Nebraska law as a noxious weed. At least 35 other states also have determined by law that Canada thistle poses a threat to the economic, social, and aesthetic well-being of the residents of their state. Canada thistle is probably the most widespread of all the thistle species and many land managers consider it the most difficult thistle to control. In Nebraska, Canada thistle is estimated to infest 460,000 acres

Biological control of Canada thistle (Cirsium arvense) in South Dakota

Canada thistle, Cirsium arvense L., is an aggressive invasive species that is found in the northern United States and not easily controlled by chemical and mechanical methods. Integrating biological control agents with other methods may improve control. This study investigated the effects of Canada thistle gall fly (Urophora cardui Diptera: Tephritidae); Canada thistle stem or crown weevil (Ceutorhynchus litura Coleoptera: Curculionidae); Canada thistle bud weevil (Larinus planus Coleoptera: Curculionidae); and Canada thistle tortoise beetle (Cassida rubiginosa Coleoptera: Chysomelidae) on Canada thistle at three SD sites 1997 and 1998, about three years after initial release. Active stem weevil larvae were found in all release sites early in the season (May, June). Bud weevils were found in a limited number of plants in July. Galls and gall fly larvae were found late in the season. Defoliation from the tortoise beetle was not noted at the one site of release. Total nonstructural carbohydrate (TNC) contents of roots were 50% lower in roots from release sites compared to TNC levels in roots from control sites at two locations in 1998. Since Canada thistle infestations rely on roots for survival, reduction of root TNC may be an important mechanism to reduce patch vigor, and ultimately, Canada thistle’s importance in the SD landscape

Canada thistle regrowth control one year after herbicide application in winter wheat

Non-Peer ReviewedA field study was conducted to evaluate the effectiveness of several herbicides for long-term control of Canada thistle growing in winter wheat. Miscellaneous herbicides were applied at the five leaf stage of winter wheat in the presence of Canada thistle (30 plants per square meter). All herbicides gave effective control of Canada thistle top growth but did not increase yields compared to the weedy check. When Canada thistle control was evaluated one year after herbicide application, three of the nine treatments significantly reduced regrowth: 2,4-D amine at 840 g/ha, clopyralid + MCPA ester at 100 + 400 g/ha, and Clopyralid at 200 g/ha. These treatments reduced Canada thistle numbers by 58, 67, and 83 %, respectively. All herbicide treatments significantly reduced Canada thistle dry matter production one year after application as measured by shoot dry weight per square meter. Clopyralid at 100 g/ha in mixture with either 2,4-D or MCPA ester at 400 g/ha, and 2,4-D amine alone at 840 g/ha reduced dry weight of thistle shoots equally. Clopyralid at 200 g/ha was the most effective treatment tested; Canada thistle shoot dry weight per square meter was reduced by 93 % one year following treatment

Temperature effect on fructan storage and regeneration of Canada thistle (Cirsium arvense (L.) Scop)

Organic farming is challenged by perennial weeds such as Canada thistle. The increasing CO2 concentration levels causing temperature increase may lead to an increased photosynthesis and as a consequence elevated storage in underground perennating organs. In this study, we analyzed fructan, the main storage in Canada thistle, in juvenile and mature plants treated with different temperatures. Low temperatures caused higher concentrations of fructan in four weeks old plants. Proximal root fragments had higher amount of fructan than distal fragments. Regenerative ability from roots with different fructan concentrations was also associated to temperature and age. This implies that the timing of root fragmentation in autumn should occur earliest four weeks before low temperatures for each location. Otherwise, new shoots would accumulate fructan causing sprouting the subsequent spring

Canada thistle [Cirsium arvense (L.,) Scop.] control in winter wheat

Non-Peer ReviewedField trials have been conducted since 1983 to evaluate herbicides for crop tolerance and Canada Thistle control in winter wheat. Winter wheat has shown excellent tolerance to a variety of herbicides, both fall and spring applied. Stage of development of shoot apices does not correlate with leaf number in winter wheat as it does in spring wheat. The Zadok scale of development may be preferable to leaf counts in winter wheat in establishing preferable time for treatment with herbicides. Preliminary indications are that the timing of application of systemic herbicides such as 2,4-D is not as critical in winter wheat as it is in spring wheat. Sampling adjacent to and in untreated Canada thistle patches demonstrated a competitive relationship between Canada thistle density and winter wheat yield. Good to excellent top growth control of Canada thistle has been obtained with clopyralid, chlorsulfuron, and metsulfuron applied in late spring. In general, top growth control of Canada thistle has been acceptable with 2,4-D and dicamba until late July. Significant yield increases of winter wheat with effective top growth control from spring-applied herbicides have not been obtained

The effects of hexazinone rates, application timing, and residue management on Canada thistle control and alfalfa seed production

Non-Peer ReviewedHexazinone is an effective weed control tool in alfalfa seed production. However, both researchers and producers have had variable success in Canada thistle control with hexazinone. The objective of this study was to determine the effects of hexazinone rates, application timing and residue management on Canada thistle control and alfalfa seed production. Two field trials were established with ‘Algonquin' alfalfa near Valparaiso, SK and Carrot River, SK in 1998. The Valparaiso trial was located on a fine-textured soil, high in soil organic matter. The Carrot River trial was located on a coarse-textured soil, low in soil organic matter. Three factors (three rates of hexazinone, three residue management treatments and two application dates) were tested in a randomized complete block design. Alfalfa seed yield and Canada thistle: density, dry matter and seed contamination, were determined in 1999. Alfalfa seed yield and Canada thistle control (density, dry matter and seed contamination) increased with increased rates of hexazinone at Carrot River but not at Valparaiso. No significant interactions between hexazinone rates, application timing and residue management for Canada thistle control were observed. However, residue management by application timing interaction was significant for alfalfa seed yield. Alfalfa seed yield was significantly higher following a spring burn at both sites

Canada Thistle

Alternate Names Synonyms Description Similar Species Family: Asteraceae Ecological Impact Biology and Invasive Potential Distribution and Abundance Management Note

Suppressing Canada Thistle Establishment with Native Seed Mixes and Resulting Cost Analysis

Canada thistle (Cirsium arvense) on conservation lands is costly and diminishes conservation objectives. This project was designed to control Canada thistle by spiking native seed mixtures. Spiking is where a native seed mixture had 3-5 native forbs that are functionally similar to Canada thistle at 3-10 times the recommended seeding density added to it. The project consisted of small-scale experiments on lands in eastern North Dakota and large-scale experiments on U.S. Fish and Wildlife land in eastern North and South Dakota. The results show that the spiked method reduced the establishment of Canada thistle immediately after seeding. The cost analysis showed the spike method was equal or lower in cost compared to herbicide control if herbicide control is: 1) 25% or less effective, 2) logistically problematic, 3) operationally more costly, 4) needed on two-thirds of the area, and 5) producing a high risk of affecting non-target species

Drought Tolerance and Perennial Weed Management

The aim of this study was to investigate the effect of controlled soil water deficits on sprouting and shoot growth of Canada thistle, coltsfoots and quackgrass. A gradient of soil water contents was created by establishing different densities of barley. The plants were harvested 14 days after watering was stopped. On Canada thistle and coltsfoots, relative water content (RWC) in leaves was measured prior to harvest and biomass of all weed shoots were recorded at harvest. In terms of shoot biomass and leaf RWC quackgrass was drought tolerant while coltsfoot was drought sensitive and Canada thistle was between the two. The barley cover crop could have had a competitive effect upon the growth of the weeds; the effect, however, was not detrimental compared to the drought effect, because relationships between initial height and the final height of coltsfoot and Canada thistle were not different among barley densities. The results suggest that the shooting from subterranean parts of broadleaf perennial weeds can to some extent be impeded by reducing soil water availability. However, the use of reduced soil water content can be challenging in fields in humid temperate regions