I've been trying for a couple of years to get rid of the stuff. We have a few raised beds, and due to injury weren't able to do much one-year and it took over. We have managed to dig out a massive amount of roots, digging down a few feet, riddling the soil and picking bits out. All appeared good this season, with just one of two marestail popping up and application of SBK appeared to kill them off well. Roofing the soil over today, after not being dug this summer, I find a fine mat of tendrils going in all directions, with the telltale signs of marestail on some ends. How do I kill this off without letting it get to the surface as a green shoot. Years ago sodium chlorate would have helped. I don't mind sterilising the soil for year, so anything that is active in the soil is needed, not something that relies on leaves being present.