April 13, 2007

If you had a musk thistle problem last year, conditions are right for a problem again this year.

Favorable rains last fall combined with short pastures are the perfect recipe for heavy thistle populations this spring.The rosette growth form is the ideal stage for controlling these plants. That means spray herbicides soon, while your musk thistle plants are still in that rosette form, so very few plants will send up flowering stalks that will require hand digging later.

Several herbicides are effective and recommended for musk thistle control. One of the most effective is Tordon 22K®, but be careful with Tordon since it also can kill woody plants, including trees. A new herbicide called Milestone also does an excellent job of controlling musk thistle. Both Milestone and Tordon also will control other weeds that usually appear later in the season.

2,4-D also works very well, but you will get better thistle control by using a little less 2,4-D and adding a small amount of Banvel to the mix.

Other herbicides also can control musk thistles in pastures — like Redeem, Grazon, Ally and Curtail. No matter which weed killer you use, though, be sure to read and follow label instructions, and be sure to spray on time.

All these herbicides will work for you this spring if you spray soon, before musk thistles bolt and send up their flowering stalks. After flowering, though, the shovel is about the only method remaining to control thistles this year.

Bruce Anderson
Extension Forage Specialist