Well, I did some research and I guess it must be slugs or snails b/c apparently that is the only pests that helenium have this time of year. I don't see any trails, but I guess I will treat this as if it is slugs. Only two of the plants are munched on.

Go out after dark with a flashlight and look, then you can target the appropriate pest. You may have to make more than one trip to catch the night feeders, start about dusk, then go again a little later if you don't find anything.

It just dawned on me that I have a few astrantias potted up. I know slugs hate those, so I sat them beside the heleniums. I have no idea if that will work or not, but it certainly won't hurt!

Thanks, morz, I think I will have to take a peek later tonight to see who the culprit is. So annoying when you are trying to baby a new plant and it is disappearing, bit by bit, right before your eyes!

Well, I went out last night with a flashlight and guess what I found? Pill bugs on my plants and having a late night snack! I have never had trouble out of them, but apparently, Helenium is irrisistable!

Right, so any bait you use would have to be something along the lines of Sluggo Plus that targets more than slugs and snails. Or agricultural grade DE.

I had issues with them one year when I had inadvertently created pill/sow bug habitat by letting a little 1" sedum spread around as ground cover, I removed that and the problem was solved.

You'll hear it said that they are only damaging in greenhouses, not so, they do like the tender growth of young plants as well as decayed plant material.