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SCOTCH THISTLE
Scotch thistle is a biennial or winter annual that reproduces solely from seed, which can remain viable for 30+ years. Therefore, the key to successful eradication is to prevent seed production. This thistle is Idaho's largest and generally inhabits waste areas, roadsides, pastures, and feed yards. Scotch thistle is not poisonous, though seldom consumed due to its spines.
Control
Mechanical: It can be controlled with cultivation. Mowing or removing the top growth will not control them unless it is done frequently throughout the season. Digging can be effective as long as the weed has not fully flowered, and it is dug up below the crown.
Herbicide: This department has seen good results in rangeland, pastures, and other non-crop areas by applying products containing clopyralid, metsulfuron, chlorsulfuron, picloram, or dicamba applied during the rosette to bolt stage. Picloram is a "restricted use" product and can only be applied by a licensed applicator. The key to success is to prevent this plant from producing seed. Herbicide control of this weed is best during the first year of growth or during the rosette stage, mid to late spring.
When choosing any kind of control method, assure that your choice is suited for your particular situation. Always read and follow the entire product label before applying any herbicide. |