Answer: The slitting and removal will only help if it is done before the vine is badly damaged. This is a moth so it can travel distances as you have seen -- the borers are just the larval stage. Sanitation is important in preventing squash vine borers, so remove all of the debris from the infested plants as soon as it is beyond salvage -- it may have eggs on it or more larvae in it so you do not want to leave it in the garden. If your compost pile is not terribly "hot" then put the debris in the trash instead of the compost pile. Rotate your plants to avoid planting susceptible crops in sequence in the same area. You might even consider skipping the squash family for a year. Turn the soil in late fall -- they overwinter at a depth of one to six inches -- to expose the overwintering cocoons to cold. Next, since you have had a bad problem with them, I would suggest using beneficial nematodes for additional control. Finally, keep an eye out for any egg masses and remove them to prevent a population build-up. Here is an article about this pest that descibes the life cycle, if you understand that you will have a better idea of how/when to try to control them. It also mentions several additional steps you can try such as planting an early trap crop if you have the space to do that.
I hope this helps!
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