We have to battle squash borers and powdery mildew as well. Last year I did surgery on my plants, too little too late... and it was nauseating pulling those horrible grubs out of the vines. This year I am spraying the plants with Bt to see if we can kill anything on the way in. If I see signs of infection, my plan B is to pull the plants and replant. I read that some gardeners have success doing that, because the insects only infest at one time of the season, and when you destroy the infected plants, the second planting will not be infected. So squash sacrifice.
For the powdery mildew, I have been spraying with a homemade recipe of 1/4 cup skim milk, 2 1/4 cup water, 1/8 tsp baking soda, few drops soap. So far, so good... the mildew seems to have subsided for the moment. I am continuing to spray once a week on my zukes and cukes.
It worked well last year, but as with the squash borers, it was too little too late. The cukes never fully rebounded.