Okay, no ducks. We need a Plan B.
Don't know how large an area is involved but you can lay pieces of glass (such as shower door panels or other tempered glass) on the area and wait a while. Between the increased sunlight and the lack of moisture plants will die - no chemicals involved. The same can be done with clear or black plastic but (in my experience) that takes a bit longer.
Someone else may chime in about chemicals. Good luck.
