It is tough to completely eradicate. Control is more like it. We have some in all our fields. There is no getting away from it. It is a native species so meant to survive. Indians used the seeds for tea/medicine. I haven't tried it yet but is tempting just to do it. Seeds survive in the soil so all your doing is turning up new seeds with tillage. Best control is late fall before it frosts with herbicides so it gets drawn into the roots. Spraying during summer does nothing but reduce the tops. Other than that it is maintain a good stand and choke it out. Lime/fertilize and good stand of grass, however on dry years like we are having here there's nothing you can do. The grass is stunted and horse nettle has a good taproot. Guess which one grows.