This year and also last year, in separate locations, I've planted butternut squash. In both places the squash leaves turned white near the center, and the white proceeds out into the veined areas of the leaf. All other squashes (acorn, spaghetti) and pumpkins are fine...no sign of this problem.
I don't think it's powdery mildew. I've had powdery mildew in the past and it eventually covers the entire leaf, then extends towards other nearby squash & pumpkins like a plague. This is centralized toward the center of older leaves (new growth on these plants is fully green...no sign of white in the center).
These areas are fairly sunny, with about 6 hrs of direct sun and both areas had very rich soil. Any ideas? Thanks,
PS In a good turnaround, the rainy weather this year has kept powdery mildew to a minimum. Last years drought made it horrendous.