Squash vine borers are probably the pest I hate the most, and they are plentiful here in South Texas. The same day I planted these I saw them flying around depositing eggs. Even on the squash planted in the garlic bed, which I would think could help keep them away with the strong smell. It usually works on most other bugs, however it didn't seem to on these squash vine borers. I spend an hour or more a day grooming my plants for these bug eggs, trying to pick them off. However no matter what you do, inevitably one will fall through the cracks so to speak and hatch. Once hatched, it will bore its way through the stem of the vine and then eat your squash from the inside out, killing the squash from that spot upward. They also tend to go after the lower part of the stem, which then will kill the entire plant vs just one section of the plant. Sprays do not work on these since they are inside the plant. So you must take drastic measures to keep your squash alive.
This means injecting BT into the stem of the plant with a syringe and needle. To do this, you want to dilute the BT according to the bottles recommendation, then put 1-2cc's into the stem above where the vine borer entered. You can find these spots by looking for the orange chewed up material oozing out of the trunk of the plant. You dont have much time once they bore their way through as they get to eating away your plant. So check daily and have syringes ready to inject. You can do this on a preventative measure as well by injecting every 10 days. BT is fully organic and will not hurt you, or bees. The bacteria targets only specific varieties of bugs, so look for the one that targets worms and caterpillars.