Field studies examined the strategies of mowing, herbicide, fertility, and all combinations on tall ironweed populations, weed biomass, pasture yield, grazing, economics, and forage quality at three Kentucky locations. Mowing was performed in July 2008 and 2009, herbicide applied in August 2008, and fertilizer applied in September 2008 and 2009 at all locations. Weed populations were measured in 2008, 2009, and 2010, and forage and weed biomass collected in May or June of 2009 and 2010. Herbicide treatments reduced weed biomass at all locations, and reduced tall ironweed stems by 64% or greater in 2009 at all locations. Weed biomass did not differ when comparing all treatments with and without mowing or treatments with or without fertilizer. Forage grass biomass produced was greatest with herbicide plus fertilizer and with the combination of mowing plus herbicide plus fertilizer at all locations in both years. Two years of grazing did not reduce weed populations. Grazing did reduce forage grass and clover biomass at one location, and weed biomass at two locations. Two locations had positive economic returns based on herbicide treatment for weed control and forge yield. Herbicide treatments reduced crude protein at one location and in-vitro true digestibility at two locations.

Tall ironweed (Vernonia altissima) and Canada thistle (Cirsium arvense) control in cool season grass pastures was evaluated in 2007 and 2008. Tall ironweed was evaluated in Fayette and Boone Counties, KY and Canada thistle was evaluated at Spindletop Research Farm. Herbicides applied selectively with a rope-wick were compared to a broadcast foliar spray. Treatments were a broadcast treatment, of aminopyralid + 2, 4-D and six rope-wick treatments: aminopyralid at three concentrations, glyphosate, triclopyr and clopyralid at one concentration each. The Boone County location had five broadcast foliar treatments: aminopyralid at three rates, triclopyr + fluroxpyr, and 2,4-D + triclopyr. The Canada thistle study consisted of the same six rope-wick treatments as the Fayette County tall ironweed study. A broadcast treatment of aminopyralid at 70 g a.e./ha was included in 2008. Studies were evaluated 1, 2, 3, 4, 8 and 52 weeks after treatment. Aminopyralid plus 2,4-D provided 86% control of tall ironweed 52 WAT. Aminopyralid at 20% v/v controlled 65% of tall ironweed. Canada thistle control 52 WAT ranged from 0 to 25% control for the six ropewick treatments.