Studies were conducted in New Jersey and Virginia to evaluate the response of ‘Aurora Gold’ hard fescue, which had undergone five cycles of phenotypic recurrent selection for increased glyphosate tolerance, to direct applications of glyphosate. ‘Discovery’ hard fescue, which had not undergone recurrent selection, was also included in the study. Glyphosate treatments were initiated in early/mid-May and applied once, twice, or three times at 4- to 5-wk intervals at rates ranging from 0.1 to 1.6 kg ae/ha. Aurora Gold was more tolerant to glyphosate than Discovery in all experiments, indicating that recurrent selection was successful in increasing glyphosate tolerance in hard fescue. Single applications of glyphosate at rates ranging from 0.6 to 0.8 kg/ha could be applied to Aurora Gold with minimal injury or stand thinning (<20%), whereas multiple applications of glyphosate could be applied at rates ranging from 0.4 to 0.6 kg/ha. The use of Aurora Gold in areas planted to hard fescue, such as golf course roughs, vineyards, orchards, and landscapes, would allow the integration of direct glyphosate applications into an overall weed management program providing potential economic and environmental benefits.

Two field trials were established in Virginia during 1998, 1999, and 2000 to evaluate long-term mugwort control with varying rates of dicamba, triclopyr, clopyralid, picloram, metsulfuron, glufosinate, glyphosate, and the dimethylamine salt and the isooctyl ester of 2,4-D. A logarithmic sprayer was utilized in the first field trial to evaluate mugwort control with each of these herbicides, and, except for metsulfuron, rates ranged from 0.28 to 8.9 kg ai/ha. Mugwort control with metsulfuron was evaluated at a lower rate range. In addition, mugwort control was evaluated with a logarithmic range of pelargonic acid rates in combination with constant rates of glyphosate, glufosinate, and the dimethylamine salt of 2,4-D. Complete control of mugwort plants and rhizomes was achieved at 1 yr after treatment with picloram at rates ≥ 0.28 kg ai/ha, with clopyralid at rates ≥ 4.4 kg ai/ha, and with glyphosate at 8.9 kg ai/ha. Greater than 80% mugwort control was also achieved at 1 yr after treatment with clopyralid at rates ≥ 0.28 kg/ha, with glyphosate at rates ≥ 4.4 kg/ha, and with dicamba at 8.9 kg ai/ha. However, all rates (≤ 8.9 kg ai/ha) of glufosinate, triclopyr, and the dimethylamine salt and the isooctyl ester of 2,4-D provided less than 50% mugwort control at 1 yr after treatment. Similar results were obtained with metsulfuron at rates ≤ 0.063 kg ai/ha. The addition of pelargonic acid to glyphosate, glufosinate, or the dimethylamine salt of 2,4-D did not significantly enhance mugwort control when compared with applications of these herbicides alone. Additionally, progressively higher rates of pelargonic acid in combination with glyphosate, glufosinate, or the dimethylamine salt of 2,4-D resulted in antagonism of these herbicides. In separate field trials conducted in 2000, reduced rates of picloram were evaluated. In these dose–response trials, picloram at 0.28 kg/ha was the lowest rate that consistently provided greater than 90% control of mugwort at 3 mo after treatment. Collectively, the results from both trials indicate that excellent long-term mugwort control may be achieved with relatively low use rates of picloram (0.28 kg/ha) and clopyralid (0.28 kg/ha), but higher rates were needed for glyphosate (8.9 kg/ha) and dicamba (8.9 kg/ha). Results also indicate that little to no long-term control of mugwort will be achieved with applications of glufosinate, metsulfuron, triclopyr, or the dimethylamine salt and the isooctyl ester of 2,4-D, even at exceptionally high use rates.

Bensulide and dithiopyr may be used in late summer–fall as a preventative treatment to reduce the potential of annual bluegrass encroachment onto newly constructed or renovated creeping bentgrass putting greens. In 1999, no herbicide treatment reduced bentgrass cover or root mass 1 mo after treatment (MAT). In April of 2000, root mass was lower with bensulide applied at 11.2 kg/ha in October and 22.4 kg/ha applied at both timings or by dithiopyr applied at all rates and timings compared with the untreated bentgrass. In April, bentgrass cover was reduced by bensulide applied at 22.4 kg/ha and dithiopyr applied at 0.4 and 0.8 kg/ha at both timings. In contrast to 1999, significant reductions in root mass were observed 1 MAT in 2000 with bensulide applied at 22.4 kg/ ha and all rates of dithiopyr. Reductions in root mass and bentgrass cover continued into April of 2001 with dithiopyr at 0.4 or 0.8 kg/ha applied at either application timing. Bentgrass cover was lower than the untreated with dithiopyr applied at 0.8 kg/ha until August of 2001. These results suggest that bensulide may be used on creeping bentgrass greens in late summer–fall with a greater degree of safety than dithiopyr.