I'm growing Boston Marrow winter squash. Last year it did great, and this year it started out great.
The problem is, after the fruits start really growing nicely (even have a few immature 10-15 pounders), the vines turn yellow and brown, shrivel up and die off.
My only thought is that it's something to do with the yard - the vines take off and grow across the grass, and I can't mow under them, so the grass grows up high all around the vines. I don't think it's high enough to obscure the sun, though.
I can supply photos if that'd help. This is killing me, as the squash were some of my best performers last year.