MANAGEMENT OF VEGETATION ON THE PAVEMENT EDGE AND ADJACENT SHOULDER. INTERIM REPORT

Herbicides were applied to the pavement edge and adjoining shoulder on two-lane highways FM 331 near Bellville on June 6, 1991, and on FM 1087 near Nacogdoches, Texas, on June 3, 1991, to evaluate their influence on vegetation control. Herbicides used included Arsenal (imazapyr), Oust (sulfometuron methyl), Roundup (glyphosate), and Velpar (hexazinone). Arsenal, Roundup, and Velpar effectively controlled roadside vegetation for 10 or 11 weeks, especially on the sandy loam site near Nacogdoches. Plant injury at both sites, particularly on the clay soil near Bellville, tended to be slightly more pronounced on the pavement edge than on the shoulder. Roundup, and sometimes Velpar, were more rapid-acting than Arsenal on most species at both sites. However, by 5 or 6 weeks after treatment, all three herbicides were usually equally effective for controlling bermudagrass, bahiagrass, bitter sneezeweed, ground spurge, prairietea croton, prickly sida, sawtooth fogfruit, slender vervain, and yellow woodsorrel. Plant species responded about equally to the different rates of the same herbicide [i.e., Arsenal at 4.7 and 7.0 L/ha (2 and 3 qt/A) or Roundup at 7.0 to 11.7 L/ha (3 to 5 qt/A)]. The mixture of Arsenal+Roundup generally injured vegetation about equally as well as Roundup at 2 or 3 weeks, but did not extend or increase the effectiveness of Arsenal alone. The addition of Oust at 280 g/ha (4 oz product/A) did not enhance the activity of Roundup at 7.0 L/ha (3 qt/A) alone.