Answer from Stan Reinke, DuPont Land Management Range and Pasture Specialist in Southern Texas:
To control weeds or not to control weeds, that is the question. The answer to this question will require some effort on the part of the pasture manager. The first task should be to scout each pasture because they are all different due to weed type, past management, degree of wetness, species of weeds, etc. Keep good notes on each pasture so that when you finish, you will be able to start analyzing what to do. As you scout the pasture, identify the weeds present; are they cool or warm season, annual or perennial, beneficial or detrimental? If you cannot identify the weed, have your county agent or NRCS agent give you some help.
With this information in hand, you can begin to make decisions about your weed control program. A good rule of thumb is if you have three or more weeds per square yard, weed control should be implemented. Remember that for each pound of weed controlled, a pound or more of grass is produced. You must also decide whether spraying or mowing would be most economical and beneficial. Typically spraying herbicides will be more cost effective than mowing. As an example, when mowing with a 40 HP tractor with a six foot rotary shredder, about 2 ¾ acres per hour can be mown. With the same tractor and a 30 foot boom, fourteen acres per hour can be treated. There is also less wear and tear on equipment with spraying.
In summary, scout the pasture, identify the weedy species present, determine if it is economically necessary to control weeds at this time, and decide on your method of control.
If you decide to use a herbicide, Cimarron Plus, Cimarron Max or Pastora will provide excellent weed control on most of the weeds present in your pastures.