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' Nelson Mining Resource <br /> Integrated Noxious Weed Management Plan <br /> ' August 2019 <br /> Page 9 <br /> Mechanical— Canada thistle is not well controlled by mechanical methods. Do not dig or hand- <br /> pull. These techniques will increase your infestation density. Canada thistle will form new sprouts <br /> at each point where its root system is broken. <br /> ' Mowing can be effective to stress the plants and inhibit flowering. Intensive mowing is best done <br /> on a monthly basis throughout the growing season. Once the plants have reached 12 inches in <br /> height, commence mowing. Mow the plants down to 2 to 4 inches in height. If the plants have <br /> ' bloomed, flower/seed heads can be removed with clippers. Be sure to bag and properly dispose of <br /> the flower heads because cut-off flower heads can still develop viable seeds. Combining mowing <br /> with herbicides will further enhance control of this weed. <br /> Chemical/Herbicides — Canada thistle is best controlled with herbicides and herbicide <br /> ' applications are best done twice per year. For Canada thistle control, spraying is most effective if <br /> done in the fall (September to early October)before the first killing frost as the plants prepare for <br /> winter dormancy. Spring spraying should be done around the time when flower buds appear on <br /> ' the plants (June). An appropriate surfactant mixed with the herbicide (refer to the label) will aid <br /> with the absorption of the herbicide into the plant and you will achieve better control results. <br /> ' As this species is often found in wet areas,it may restrict the use of certain herbicides. An aquatic- <br /> safe approved herbicide is a great quality to have in an herbicide when applying near any kind of <br /> riparian areas(near a stream or river)or drainages. Care must be taken to avoid spraying herbicides <br /> ' near water unless they are specifically labeled for aquatic use. An aquatic-approved herbicide is <br /> required when applications will be made over water or encounter surface water. Combining <br />' mowing with herbicides will further enhance control of this weed. <br /> Biological—The primary biocontrol agent currently in use against Canada thistle is the stem-gall <br /> forming fly(Urophora cardui) and is effective on large infestations and when combined with other <br /> control methods. This agent is not effective in killing the plant but may weaken the plant, making <br /> it more susceptible to other stresses. <br /> 3.2.4 Musk Thistle <br /> Cultural — Establishment of selected, aggressive grasses can be an effective cultural control of <br /> musk thistle. <br /> Mechanical — Musk thistle can be controlled by several mechanical methods: cutting, pulling, <br />' mowing, and clipping. Mechanical control (e.g., mowing) is best done once or twice in the spring <br /> to early summer as the plants bolt,but before the plants flower(roughly April through early June). <br />' Grubbing or digging out rosettes, cutting flower stems, and hand-pulling can be effective as well. <br /> Rosettes can be cut out of the ground with a sharp shovel. Be sure to cut below the root crown <br />' level (about 1 inch below the soil surface). Be sure to sever the root completely to kill the plant. <br /> Digging out the plants is most effective during the rosette stage, but if the plants have already <br /> bloomed when you cut or pull them, remove the flower/seed heads with clippers and be sure to <br />