Phil: they can certainly be a problem for folks that haven't taken necessary precautions, such as crop rotation. However, the plants, in discussion, root very quickly with some moist soil placed up near and around the cut. Also at the very time of the cut, one should view if any larvae are present and simply remove them. Also many small gardeners simply interplant pumpkin with corn. Seems to work quite well.
Vine borers are far more prevalent with use of insecticides.
"When in doubt, empty the clip."