Something is slicing through my morning glories about 5" up from the ground, leaving the vines hanging on their string to die. It only happens on one side of my deck. I sprayed for moles there, because it's been happening since Spring. The morning glories get about 3' tall, and it looks like a clean slice through the stem. The first time, the plants were gone, so I thought it was some kind of critter. Now I'm thinking it's some kind of cut worm, because the plants are still in the ground, and the vines are still dying on the twine = nothing's been eaten. What do you make of this?