Well...this happened to me here in Florida as well...It looks like the Squash Vine Borer payed your pumpkins a fatal visit. They eat your stems from the inside. The black poppy seed stuff is their excrement. You can always tell they are in there because of the frass near the entry hole. The leaves wilt and then the whole thing starts changing to yellows and browns as if it were diseased. DO NOT COMPOST these critters. I have not found anything yet that keeps them away either. Hope it helps.

Here is a link that might be useful: Kovar Garden YouTube Channel

I was hit hard last year in coastal NC with my squashes and pumpkins. I saw a good video on how to stop those pests, but have not tried it yet. Basically you pour about a tablespoon of organic Neem oil on the open part, wrap with two 4X4 gauze pieces, and then cover that with a strip of 4-5" aluminum foil wrapped around the stem. Last year I did not know about this, so I tried to remove the worm inside the stem with some hemostats. It lasted long enough to ripen up the squash, then I burned them so they would not infect my compost pile. Good luck!

Definitely squash vine borer. I plant a second crop on first of July because I know it's just a matter of time before they kill the early crop.

I have one very aggressive pumpkin this year that is fighting SVB with loads of secondary nodular roots.