Tumbleweeds in Rock

[sheerrocko]

What herbicides do you guys recommend for new tumbleweeds. I need to spray a quarter of acre of landscape rock that has these nasty things popping up all over. Would a mix of pre emergent and post emergent herbicides work best?

I have sprayed the area using a mixture of 41% glyophosphate. That stunned many of them, but tons more are on their way.

Thanks
Rocko