From UT Extension:
Management in Pastures and Hay Fields
As is the case with most other weeds, prevention is an important component of an overall management plan. In the case of horsenet-tle, feeding infested hay is the one of the primary ways the weed is introduced into a field. If possible, buy clean hay of known ori-gin. Monitor areas around hay rings for development of problems and, if possible, spot treat these areas before the weed spreads to the rest of the pasture. Also, because horsenettle seed can pass intact through an animal's gastrointestinal tract, avoid immediate movement of cattle from heavily infested pastures to uninfested ones if at all possible. Clipping will slow the growth of the plant and, over time, deplete carbohydrate reserves in the roots and rhizomes and stimulate the growth of new, more palatable grass; how-ever, clipping will not control horsenettle.
Timely application of a herbicide is usually required for effective control. Several herbicides such as 2,4-D, Banvel/Oracle (dicamba), and Rangestar/Weedmaster (2,4-D + dicamba) will give various degrees of weed top kill but they do little to the roots and rhizomes. Currently, the University of Tennessee recommends Milestone (aminopyralid) or ForeFront (aminopyralid + 2,4-D), or Grazon P+D (picloram + 2,4-D) in approved counties. Grazon P+D is a restricted-use herbicide. University of Tennessee research has shown that the optimum time for application of these herbicides is at the flowering stage, prior to formation of berries. Be sure to thoroughly read the herbicide label prior to application. Also, consult the Pasture and Forage section of Publication 1580, Weed Con-trol Manual for Tennessee, for application rates and instructions, precautions and other useful information. A copy can be obtained at your local UT Extension office.
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