With all due respect, why do you delude yourself? It is the SVB, you just have not found the frass or the cavity yet.

Glib, no offence taken, but I tried looking along all major vines and could not find SVB indications. Also, does SVB cause wilting that is only during the hot hours? The plant perks up by late afternoon.

Not necessarily. In the intense heat of the Deep South, it is perfectly normal for plant leaves to droop a bit (or more) in the mid to late afternoon. I have read that they are protecting themselves from lasting damage. They perk up after night falls and it cools a bit (all the way down to 72, if we're lucky).

If it was SVB, your leaves would not recover and you would see obvious signs of the stems being eaten to tunnels and mush near the ground.

I'm growing Black Futsu this year (like I do every year) in a raised bed, and it is struggling. The well draining soil and intense, prolonged heat as donnabaskets says, is taking its toll. We've had no break, no "real" rain...the squash I have planted in mostly (but not totally) clay that is heavily amended and very well mulched is doing super. ( have mulched the stuff in the raised beds too, but the exposure to weather and sun is different) the clay is holding the right amount of water for a long time and I've seen little struggle with the ones in the ground so far.