I think that there is some discrepancy between recommendations from PA, MD, NJ universities or extension services. I read several of them this morning. Rutgers agrees that there is only one generation UNLESS weather conditions are favorable and that USUALLY plants grown after July 1 will not be infested.
PA says that there is only one generation and MD says 1-2. MD suggests planting either very early or late. Now that's helpful isn't it? So in other words plants may be attacked either early or late and it's a matter of luck whether you get a harvest or not.
I am sticking with planting both early and late and I always get summer squash. Yes, the early ones always get infected but not until after I have harvested a lot of squash and by then the second crop is usually growing well. However a late crop is susceptible to powdery mildew so it does not usually produce as well as the first crop.
Here is the Penn State link.
https://ento.psu.edu/extension/facts...ash-vine-borer