Posted: 22/08/2016 at 18:47
glyphosate will be as effective as anything else....suckers are mainly soft and green. However this is a real problem Dave. Normally regular cutting off, mowing for example, would weaken most growths but sumacb reaponds witb even greater vigour.
Sbk should work now on the main trees though.
I would spray every shoot seen and be persistent.....starting asap.