I've got some runners (hope that's the right phrase) coming under the
fence from next door's plum tree and shooting-up in several unwanted
places in a flower bed in my garden. Apart from cutting the runners
back to ground level - is there anything else I can do to get rid of
them without having to dig them all out (they're pretty inaccessible).

I've also got something similar from a viburnum in my own garden which
is popping-up all over the place.

Thanks,

Michael