Control of Horsenettle (Solarium carolinense) Fleshy Roots in Pastures

The effectiveness of dicamba (3,6-dichloro-o-anisic acid), picloram (4-amino-3,5,6-trichloropicolinic acid), and triclopyr [(3,5-6-trichloro-2-pyridinyl)oxy]acetic acid and mixtures of these herbicides with 2,4-D [(2,4-dichlorophenoxy)acetic acid] for the control of horsenettle (Solanum carolinenseL.) in Kentucky bluegrass (Poa pratensisL.) pastures was evaluated at three different field sites in Southwest Virginia over a period of 3 yr. Picloram applied at 0.6 and 1.1 kg/ha significantly reduced horsenettle roots, as indicated by a 98% reduction in shoots 1 yr after the first annual application. No shoots emerged within 18 months after three annual picloram applications. There was no significant difference between picloram applied alone and in a mixture with 1.1 kg/ha of 2,4-D. Three annual applications of triclopyr at 3.4 kg/ha reduced horsenettle shoots from 82% to 92%. The 3.4-kg/ha rate of triclopyr was slightly more effective in controlling horsenettle roots than was triclopyr at 1.7 kg/ha alone and in mixture with 1.1 kg/ha of 2,4-D. Dicamba at 0.6 and 1.1 kg/ha reduced the horsenettle shoots by 74% and 81%, respectively. The reduction was similar from mixtures of dicamba (0.1 and 0.3 kg/ha) with 2,4-D (0.4 and 0.8 kg/ha). There were no effects on the bluegrass forage that could be attributed to the herbicides.