Pumpkins in North TX??

[BB_TX]

The last 2 yrs I have planted some pumpkins for the grandkids to pick for haloween. But limited success. Last yr I had 6 vines and only had 4 pumpkins. This yr I had 5 vines and only 1 pumpkin. The pumpkins I do get are nice size, just not many of them. Vines look great running out 20' or more. Lots of male blooms. Not many female blooms. And the female blooms die before the fruit was much larger than pea size and the flower never opens. No obvious signs of insects. Any idea why the female blooms do not mature?