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TURKEY CREEK CD's Noxious WEED CONTROL PROGRAM FOR PUEBLO COUNTY PAGE 6 OF 10 <br /> present. Also avoid application during heavy upward sap flow in the spring when sap <br /> flowing out of the wound will prevent good herbicide absorption into the tree. <br /> Russian Knapweed (Acroptilon repens): <br /> Russian knapweed is a perennial plant with a creeping root system. These plants are long-lived and <br /> will grow and spread year after year. Seed viability in the soil is approximately 3 years. Russian <br /> knapweed spreads mainly through its extensive creeping root system and will form dense colonies. <br /> New shoots will emerge from any root fragmentation. While it is important to stop seed formation, <br /> with this plant, it is most important to stop its vegetative spread. Russian knapweed is allelopathic, <br /> which means it contains a toxic substance that inhibits the growth of competing plants. Russian <br /> knapweed is toxic to horses. <br /> ❖ Russian knapweed is not well controlled by mechanical methods. Do not dig or hand-pull. <br /> These techniques will actually increase your infestation density. Russian knapweed will form <br /> new sprouts at each point where its root system is broken. <br /> • Mowing can stress the plants and inhibit flowering. Mowing is best done several times <br /> between spring and summer(May-June)as the plants bolt but before flowering. <br /> • Revegetation is very important in Russian knapweed control as the desirable plants will <br /> provide competition. Depending upon the site,tillage may be necessary to overcome the <br /> residual allelopathic effects of Russian knapweed before reseeding. (Refer to the <br /> revegetation guidelines section of this management plan for further information.) <br /> ❖ Russian knapweed is best controlled with herbicides.Herbicide applications to control Russian <br /> knapweed are best done twice per year: once in the spring before plants have bloomed(April- <br /> May)and again in the late fall (late September to early October)before the first killing frost as <br /> the plants prepare for winter dormancy. Russian knapweed is very susceptible to fall-applied <br /> herbicides. An appropriate surfactant mixed with the herbicide(refer to the label)will aid with <br /> the absorption of the herbicide into the plant and you will achieve better control results. <br /> Musk Thistle(Carduus nutans) <br /> Musk thistle is a biennial plant. Its life cycle is completed in two growing seasons. In its first year, it <br /> is a cluster of leaves at ground level called a rosette. During its second year it bolts,forming an <br /> elongated flowering stem. Musk thistle only spreads by seed so it is very important to stop seed <br /> formation. Each plant can produce up to 100,000 seeds. On average,plants produce about 10,000 <br /> seeds. Seed viability in the soil is approximately 10 years. <br /> ❖ Musk thistle can be controlled by several mechanical methods: cutting,pulling,mowing, and <br /> clipping. Mechanical control is best done in the spring before the plants flower(roughly April <br /> through early June). When working with these plants,remember to wear appropriate clothing to <br /> protect yourself. gloves, long-sleeves, long pants, and shoes with socks are recommended <br /> because the spines of these large thistles are very sharp. <br /> • Digging out rosettes, cutting flower stems, and hand-pulling can be done anytime you find <br /> them. Rosettes can be cut out of the ground with a sharp shovel. Cut them just below the <br /> soil surface(about 1 inch) and be sure to sever the root completely to kill the plant. The <br /> plant can also be cut out or pulled by hand after bolting but before it flowers. If the plants <br /> have already bloomed when you cut or pull them,remove the flower/seed heads with <br /> clippers and be sure to bag and properly dispose of the flower heads because cut-off flower <br />