I presume you had squash vine borer?

When I cut the vine open there was a fat white worm. Any ideas how to prevent this?

Where I am (Southern WI) we need to spray around the base of squash plants in mid-late June for vine borers (preventative). Not sure what the timing would be in Florida.

Let me know what you use, please! Mine were big and producing but the borers chewed into the stem.

I use Malathion because I have it on hand. I can mix it in my one gallon pump sprayer and spray the base of each vine near the soil line. Seems to work as long as I get the timing of the application right. Luckily for me our state of WI puts out a Pest Bulletin by e-mail and normally mentions when the vine borer adults are present and laying eggs. I just read their message and spray when it tells me to. Hopefully Florida does something similar.

I have had vine borers destroy my summer squash (patty pan) and also jumbo pink banana squash. Butternut is supposed to not be hit as hard by vine borers.