2018 Information. The Canada thistle rust fungus (Puccinia punctiformis) was introduced into Oregon in 2018 to control Canada thistle. Light to medium infestations can be controlled with repeated mowing at 21 day intervals. Canada thistles in pastures don’t just look ugly, they cause economic harm with yield losses approaching nearly two to one. Two biological control agents have been introduced for Canada thistle control, and a third was introduced accidentally. It is difficult to control because its extensive root system allows it to recover from control attempts. Canada thistle is difficult to control because it is a perennial plant with a deep taproot (Photo 6). Success requires a sound management plan implemented over several years. Stems may branch near the top. Larvae Thistle Stem Weevil Courtesy www.oregon.gov. Dormant. Use tested seed when planting row middles to minimize the risk of contamination with weed seeds (Figure 2). Mowing infestations can increase densities as this perennial species can reproduce via seed as well as rhizomatous sprouts. Add about 1 teaspoon (0.5 to 1 gram) of ground leaves to the upper leaves of plants that have emerged in … By Debbie Furber. • Repeated mowing suppresses in Canada thistle forages. The plants are 1-3′ tall, and leaves attach in an alternating pattern up the stem. Flowers - Small lavender, rose-purple, sometimes white flowers are 1/4 to 3/4 inch wide, in groups of 2 to 5 at the end of stems. Dr. Wilson reported that fall herbicide applications caused changes in sugars stored in the roots of Canada thistle, and decreased the chances of the weed surviving the winter. Bloom. Canada Thistle and Its Control (Classic Reprint) | Hodgson, Jesse M. | ISBN: 9780260702432 | Kostenloser Versand für alle Bücher mit Versand und Verkauf duch Amazon. Control is considered to be prevention of seed production. However, Canada thistle will continue to flower after mowing, so repeated attempts must be made throughout mid and late summer to prevent overall seed production. The plant is beneficial for pollinators that rely on nectar. Spray at early bud stage or in early fall. Canada thistle is a creeping perennial that reproduces from vegetative buds in its root system and from seed. Several herbicides are effective and recommended for thistle control. However, it is difficult to distinguish the two flower types based on appearance. Roots - The vigorous roots will grow 3 feet wide and 3 feet deep. Weed Identification. Step 3. Reporting . To optimize perennial broadleaf weed control, herbicide selection and use must be co-ordinated with crop rotations and cropping practices over the long term. Typical leaf length is 3-4″ inches, although they may reach up to 8″ long and 1″ wide. Biological control insects are not considered a recommended means of control in Minnesota at this time. One treatment or a combination of treatments may need to be used to control populations depending on the site. Flowers are pink, bristly, 1/2 inch long and wide. Canada thistle is an invasive species. Similar species: Canada thistle is distinguished from all other thistles by creeping lateral roots, dense clonal growth; and small dioecious flower heads (meaning male and female flowers are produced on separate plants). Canada thistle is diecious, which means male and female flowers occur on separate plants. Hadroplontus litura, or the Canada thistle stem weevil, is a biological control agent that attacks Canada thistle by larval feeding within the stem, opening the plant up for secondary damage from other organisms such as opportunistic pathogens. Thistle Stem Weevil (Ceutorhynchus litura) Generations per year: One. Weevil, which first was released in North Dakota in the 1970s tall, leaves. 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