Sigh. Probably SVBs. Look at the base of the damaged stem for frass from the embedded larva. If fact, I think I see a split stem inside of which one was doing the damage. Neem? Nope. It's a LOT harder than that. Seems like every other day there is a frantic and hugely depressed post here about Squash Vine Borers. SVBs are THE WORST ENEMY of vegetable gardeners. Welcome to the club. I get depressed just talking about them.

The best way to protect the plants is with a vine cover. Keep the buggers from getting to the squash in the first place. Of course, then you're talking about manual fertilization, etc. Also, don't put a cover over a bed that has recently suffered from SVBs. They're in the soil, and you'll just trap them underneath with the plant.

Another good way to avoid having plants damaged by SVBs is to move to the west coast.

Do a little reading about them. There is loads and loads of info available.