Kinda looks like that is what you have. Running a thin wire up the stems to pierce the larva is one control method, injecting Bacillus thuringiensis - Kurstaki into the larvas tunnel is another. This link gives others, although not all will necessarily be organic.

Here is a link that might be useful: Squash Vine Borers

So sorry--lost all our curcurbits one year. That's why I successively plant now. The nasty bugs are only there a short time period. You can try to protect them by covering as much of the vine with soil as you can.