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.

Canada thistle is an aggressive perennial weed throughout temperate areas for both the northern and southern hemisphere. As various single tactics have shown limited success in controlling this weed, I believe that a combination of different stress factors is necessary for effective sustainable control of Canada thistle. This study evaluates the competitive abilities of tall fescue grass and crownvetch in conjunction with a thistle feeding insect for Canada thistle control. The goal of the study was to determine what levels of the herbivore and plant competition are needed to suppress Canada thistle. Field studies were conducted to determine the effects of multiple stresses caused by defoliation and plant competition on growth and survival of Canada thistle (<i>Cirsium arvense</i> Scop.). Plant competition was from a cornbination of tall fescue (<i>Festuca arundinaceae</i> Schreb.) and crownvetch (<i>Coronilla varia</i> L). Artificial defoliation was used to determine the influence of level and frequency of defoliation in combination with plant competition on Canada thistle. The effects of various densities of a defoliator, <i>Cassida rubiginosa</i> (Coleop:Chrysonlelidae), in the presence and absence of plant competition were also determined. A three-season study determined the combined effects of <i>C. rubiginosa</i> and plant competitors at various densities on the growth and productivity of Canada thistle plantings of various ages. / Ph. D.

The aim of the present diploma thesis is to widen knowledge of the chemical regulation of weeds in row crops. To establish the effectiveness of herbicides, we set up a small lot at a carefully chosen spot in the potato-growing region near Strakonice. We conducted a comparison of the effects of three herbicide combinations on two potato varieties (Red Anna, Laura). Two combinations proved pre-emergent (Afalon 45 SC+Command 36 SC; Sencor 70 WG+Command 36 SC), one post-emergent (Titus 25 WG). Subsequently, we evaluated economic costs on weeds regulation and suggested preliminary measures to be taken.