April 24, 2009

Rosette growth stage of musk thistle.

If you had musk thistles in your pastures last year, the odds are you'll have them again this year. Favorable rains last fall combined with short pastures are the perfect recipe for lots of thistles this spring.

Chemical Control

The rosette growth form develops in spring and is the ideal stage for controlling these plants. Spray herbicides soon, while your musk thistle is still in the rosette form, and few plants will send up flowering stalks for hand digging later.

Several herbicides are effective and recommended for musk thistle control. Tordon 22K is one of the most effective herbicides, but use it with caution as it will kill woody plants, including trees you might want to keep. A new herbicide called Milestone also does an excellent job of controlling musk thistle. Both Milestone and Tordon also will help control other weeds that usually appear later in the season.

While 2,4-D also works well, you will get better thistle control by using a little less 2,4-D and adding a small amount of dicamba to the mix. Other herbicides for control of musk thistles in pastures include Redeem, Grazon, Cimarron, Ally, and Curtail. As with all herbicide use, be sure to read and follow label instructions, and be sure to spray on time. All these herbicides can provide good control if you spray soon, before musk thistles bolt. After flowering, the shovel is about the only method remaining to control thistles this year.

For product rates and efficacy ratings for musk thistle control in pastures, also see the 2009 Guide for Weed Management in Nebraska, available online and from your local Extension office.

Bruce Anderson
Extension Forage Specialist