The Fall is the best time to spray musk thistle. From October 1st to ground freeze, use the chemicals Tordon 22K or Milestone. For spraying during the Spring, when temperatures are warm enough for growth and center of the rosettes are green use one of he below chemicals. Tordon 22k - Milestone - Escort XP or 2-4D. For more information please call the Phillips County Noxious Weeds Department M-F, 8:00am-5:00pm at 785-543-6870.