Two field studies evaluating horsenettle control were conducted from 1997 to 1999 to examine the efficacy of various fall-applied herbicides and rates and to evaluate the effect of the stage of horsenettle senescence on the effectiveness of fall glyphosate applications. The herbicides and rates evaluated in the fall herbicide efficacy study included 1.1, 2.2, or 3.4 kg ai/ha glyphosate, 1.7, 2.2, or 3.4 kg ai/ha glyphosate-trimesium, 0.6, 1.1, or 2.2 kg ai/ha dicamba, 0.06 plus 0.16, 0.09 plus 0.2, or 0.17 plus 0.44 kg ai/ha BAS 654 plus dicamba, respectively, or 2.2 kg ai/ha glyphosate plus 0.6 kg ai/ha dicamba. The highest horsenettle control in the following spring was observed with all rates of glyphosate or glyphosate-trimesium, the highest rate of BAS 654 plus dicamba, or glyphosate plus dicamba. In the study on the horsenettle stage of senescence, 2.2 kg ai/ha glyphosate was applied at stages of senescence in the fall. The presenescence stage reduced horsenettle shoot density from fall to spring and provided the highest level of control in June and July of the following year compared with plants that had already begun leaf color change and leaf drop.
Nomenclature: BAS 654, 2-(1-[([3,5-difluorophenylamino]carbonyl)-hydrazono]ethyl)-3-pyridinecarboxylic acid, proposed common name diflufenzopyr; dicamba; glyphosate; horsenettle, Solanum carolinense L. #3 SOLCA.
Additional index words: Fall herbicide applications, perennial weed management.
Abbreviations: COC, crop oil concentrate; NIS, nonionic surfactant; POST, postemergence; UAN, urea ammonium nitrate; WAP, weeks after planting.