What happened to my squash?
I had two yellow squash plants and got a single squash from each one. After that, the leaves were wilted every morning but sprang up after a couple of hours and this went on for a few days before the plant completely went limp as though it had boiling water poured on it. This happened to one plant first, then the other after the first one was dead. I pulled the second one up and saw this damage, I am assuming from some kind of insect. I have two zucchini plants in the same area and am wondering how to prevent the same thing happening to them.
At first I was suspecting that your squash plants were not taking in enough water in hot weather which is a common problem even if water is plentiful but it doesn't look like that is the problem.
You problem most likely is due to the Squash Vine Borer. Look for darkened spots at the base of the stalk then slit it open to reveal the borer grub. See the below listed links for a more detailed explanation. I have also listed a link on squash bacterial wilt; but it does not appear to be your problem.
Zucchini is also susceptible to the borer. The best treatment is prevention before the eggs are laid by the use of physical control to exclude the borer, organic or synthetic pesticides, or cultural controls. The links will address the practices also.
Thank you for giving us the opportunity to help with your problem in some way and don't hesitate to contact us again if necessary.