I have researched how to manage squash vine borers and there is remarkably little scientific research that will help the home gardener. Big commercial growers use a chemical drench, but that’s no help for organic gardeners. I have heard of wrapping the base of plants with aluminum foil. Maybe that works, but I have not found any rigorously controlled studies of the methods.
Physical barriers and BT (Bacillus thuringiensis) appear to be the most effective management methods. Barriers such as row covers in the spring will help prevent the moths from laying eggs. Regular foliar spraying of BT (Bacillus thuringiensis) appears to be the most effective way to manage squash vine borers. There is persuasive research that BT works on cucurbits like mirlitons (chayote). Start spraying the vines early in the spring and continue throughout the season (don’t mix with oils because they can kill the vine in hot weather).
Some people inject the BT into the vine with syringes, but this will not work because larvae don’t consume BT and it will only kill the larvae if it reaches their gut.
Click here for a short overview of vine borers and how to manage them.
Click here for the best article I found on BT for managing vine borers.
Click here to read about how it is safe for humans to use on crops.