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-II~TSGRA'TED WEED MANAGEMENT of CANADA.THISI'LE for Home Ciwners. No single control method should be used in ti managing weeds.. A combination of methods (IPM) should be used: 'An integrated pest management plan deals with prevention as well as control. Eradication of weed species is not usually a practical goal but reducing infestation to manageable levels should be the objective. CANADA'~~.F (Cirsium arvense) is acolony-forming perennial from deep underground and extensive horizontal roots. Stems are 1-4 ft. tall, ridged, branching above. Leaves are alternate, lacking petioles, oblong or lance- shaped, divided into spiny tipped irregular lobes. Flowers are unisexual, on separate plants; flowers purple in heads 1/2-3/4 inch in diameter; involucral bracts spineless. Cultural Plant competition is an effective way to prevent the invasion of Canada thistle. Proper management of perennial grasses will inhibit the establishment of this weed. Overgrazing is a major cause of perennial ' weed invasion. In Douglas County, one horse requires 35 to 40 acres of pasture land if no supplemental feed is provided. Residents should wnsider the above facts when planning recreational or hobby activities as it pertains to Gorses. A general rule of thumb to prevent overgrazing, is the take-half leave- half principle. A stand of grass will maintain or even improve its condition if no more than one-half of its annual production is used. In other words, animals could graze until, on average, Eifty percent of the grass has been utilized. Animals would then be removed until the vegetation recovers its original height. Other cultural methods include: • fertilization when necessary (A soil test is the best way to determine fertilization on a site. Contact the Douglas County Extension Office for soil test kits.) • water management • where the perennial vegetation has been depleted, reseeding adapted varieties is recommended • disturbed areas should be revegetated as soon as possible to prevent weed invasions Biolo ical Insects are being utilized as a means for long-term management of weeds. In Colorado, insects have been released on an experimental basis to wntrol Canada thistle. At this time, some are available to the general public. A weevil and a fly attack the Canada Thistle plants. The costs are about $100/100 adult weevils, and $75/l00 adult [lies. The weevil should be released in April and/or May. The fly in May and/or June. Mechanical One season of intensive tillage from spring until freeze-up will usually eliminate over 90% o[ Canada thistle. Cultivate every 14 to 21 days. Cut thistle plants no more than 4 inches below the surface. Persistence and proper timing are important. Mowing would weaken the plant, but not kill it. Mowing at least as often as the suggested tillage treatments. Chemical Homeowners should plan Eor a spring and fall treatment. Established plants may require about 4-5 years of treatments for desirable control. Always read and follow the label! • 2,4-D amine @ 3 tablespoons/1000 sgft. (spring @ late bud and in the fall.) • Roundup @ 3 ounces/1000 sq. ft. in • the spring at the bloom stage. • Banvel can be used if treatments are at least 2x the height from a tree trunk and the daily high temperature is less than 85F for the next three days.Mix @ 1.5 tbslgal/1000 sgft. at the same timing as the 2,4-D.