Can you send a CLEAR picture, a close up type is best as it gives clear indication what is ruining the Pumpkins.
It could be anything from Butterfly eggs that hatch into caterpillars and these gnaw their way through every bit of nice juicy greenery they can crawl over,
Could be Aphids, these are green, black flies or it could be something different from these I mention.
Until you get a photograph sent in, you can kill the eggs by hand, use rubber washing up gloves IF you don't like the idea of things like that on your hands, you could spray with a diluted mixture of warm water and dish washing liquid, do that after you hand kill the eggs as it will get rid of the insect laying the eggs and wash away their sticky remnants from whatever laid the eggs. you need to keep this method going to keep on top of the control BUT, it can be done by vigilance and strict spraying with the dish soap.
Hope this helps you for now and you can get back to us with a picture soon.