As I mentioned on your other post of this question we really need more details. It could be anything from normal to a disease of some sort to a pest infestation.

What color is this sticky substance? Is it all over the leaf surface or just in spots? Is it also on the stems? Does it seem to be damaging the leaves or do they look normal? Can you post a picture? Is the plant blooming and setting fruit? Is the substance on the fruit as well? What pests are visible on the plants?

Aphids exude a sticky substance called honeydew but you would have to have an obviously severe aphid infestation to make it really noticeable. Whiteflies, also obvious, will drain the natural sap from the plants and deposit it on the leaves. Both those are just guesses.

So examine the plants for pests and see if that solves the problem.

Dave

I tried to post a picture, but it appears I don't have the know-how to accomplish that task.

A few answers: I think it's a clear substance...shiny. It's just in areas of the patch now. Yes, the vines are blooming and setting fruit. At least a couple melin have the sticky stuff on them. From the 2 plants, I have identified 18 different melons. I have lost a couple that split open, a couple that have wrinkled up and withered after they'd started to grow. I do believe it is a case of aphids. I was in the patch checking and picking a melon this morning and when I came out, I realized that I had many very small crawly things on my arms. I'd say infestation, it is!

I tackled the situation with horticultural oil spray, doing the best I could to hit the underside of the leaves with the spray. Do you suppose that will be enough to knock back the population?

Can aphids destroy the vine? I already lost my cantaloupe this year before I was able to harvest any because of bacterial wilt. I'm hoping that the watermelon will make it.

Do you have trees in the area? I've had sticky stuff falling from trees, also honeydew from aphids eating the trees. It ends up on everything else as well, though.