I'm having the same problem. The other day I found a little "blob" of a light brownish, almost terra cotta looking, glob of hard material on one of the vines. It almost looked like the start of a hive of some kind and crumbled when I pinched it off. Earlier in the season I removed a black and yellow striped worm/caterpillar from the pot they're in but it seemed to be in amongst some licorice plants that are also in the pot.

earlier I had problems with leaf miners eating the leaves of my Morning Glory.. I since the sprayed an insectiside on the entire vine and that took care of that problem. it's now looking pretty nice again and actually keeping leaves long enough to grow to the larger expected size.

I tried spraying them with an insecticide also, but vines are so thick it is hard to get all areas. However the leaves are very large and otherwise healthy....wierd. Only thing I have ever noticed on them is real small ants?

The pest that is devouring your Morning Glory must be inch worms, they are devastating mine.
They are hard to spot and on the underside of leaves. They are very light green matching the color of the underside of leaves and they range in size from 1/8" to 1 to 2 inches.
I have sprayed over several days and with increasing concentration of Diazinon but they must be drinking it because they keep eating my MG which it looks now as if it's been shot with shotguns, not a single leaf intact and some of the larger leaves have only the "arteries" left.
I have declared war on the creeters, I go out at night with a flashlight and kill them by hand, one by one and I'm slowly making progress.

I've had japanese beetles eating my morning glories, but they seem to prefer my green beans. I've also found the JB on my hollyhocks.

My Manhattan terrace garden has bloomed with MGs several years past but this year I too am finding shot-gunned leaves and a total lack of blooms. Finally, a few blooms appeared yesterday. But some curled-up buds yet to open had tiny holes in them with a small green worm inside. This is the first time I've actually seen a real pest. While my leaves are huge and numerous, I guess they are supplying many midnight snacks based on the holes. I just wish I could get a few flowers to show before there are more holes than leaves.

Here is a link that might be useful: