earwigs, cutworms, various beetles or weevils, someone playing games with you.

jc, go out at night after dark with a flashlight and look - you'll answer your own question.

I have the same problem! I'm in Canada - zone 3a

Most my plants have large holes in them. Some of the holes are 2 1/2 feet off the ground (trumpet vine). No bugs on the leaves, no slime trail near the plants on the ground.

A tomato plant in a large barrel is fine.

I've checked for worms on the leaves - nada. I do have mulch (shredded wood pallets) and barrier cloth beneath most of my plants however plants without the mulch are also being chewed.

Huge bergenia leaves are half eaten away. It's crazy that I can't find evidence of what does it.

Like morz8 said, many of these insects are nocturnal so you'll need to go out after dark to find them.

I went out last night and found only one sow bug about an inch off the ground on a green bean seedling. At least now I know they can climb. And there were plenty of sow bugs on the ground...I put them there, they came with the last load of compost I spread under the plants. That may have been a fatal mistake. I'll keep looking every night to get a feel for their climbing ability and start the process of squishing every sow bug I see. But by the amount of damage I've seen, especially on the upper green bean leaves, there should be hordes of sow bugs on every plant. And I only found one.

The damage is more like what slugs can do, so I'll be watching for slime every night.

Some 3 foot tall green beans in containers, elsewhere in the yard, had their upper leaves mostly chomped off. I suspect birds but I haven't seen any. How to keep the birds off, am I going to have to cover the plants with screen type netting?

jc

My noctural excursion this evening (salt shaker and plate of beer in hand) found a few small slugs on the bergenia, but nothing on the hostas or trumpet vine.

OK, did either of you make more than one trip? Sometimes necessary to catch the right culprit. Half a large leaf surface or upper parts of pole beans missing sounds more like climbing cutworm/caterpillar damage to me.

Our weather is most likely different, but here in the slug capital of the world, I can find slugs beginning right about dusk, certainly within an hour of it becoming dark - if slugs were the problem you should have found them.
And I think you could lose the salt, trade it for ammonia + water. I carry two weapons on my nighttime flashlight hunts...a spray bottle of 1 part household ammonia to 3 parts water (kills slugs in a heartbeat when you spritz it on them and unlike salt it doesn't harm foliage so quite satisfying when they drop dead off your favorite plant), and my oldest pruners for snipping cutworms in half.

I like the amonnia and water trick. I'll give it a try. Thanks.

I've been out looking late at night again and found a few more very small sow bugs finishing off some bean seedlings...but the damage (my best hope for cucumbers this year, 3 inch high seedlings with good leaves...leaves vanished completely-no debris-) is greater than small sow bugs could accomplish. Where would a sow bug store a 2x2" leaf? There would be giant piles of sow bug excrement everywhere!

No sign of slime, and slugs usually leave pieces of shredded leaves. I don't live in a very sluggy area, although there is a cooler time of the year where I've found a few. I'll remember the ammonia and water trick.

I didn't know cutworms could climb, are they active at night also?

BTW, here's a good trick for finding cabbage loopers, especially on tomato plants. Just flick the leaves or shake the stems and they drop like flies. Once on the ground they like to rear up and wave their heads, making them easy to spot.

JC, yes there are climbing cutworms and they are nocturnal feeders, like many of the caterpillars are. I never have the type that can be controlled by collaring seedlings for protection, mine climb like acrobats. They can take new foliage at eye level on rhododendron down to the mid-vein in one evening :(

Here is a link that might be useful: UCDavis, climbing cutworm

Hmm... you say that the the tomatoes and onions arent touched? You could try a spraying a 'soup' made from onion and tomatoe leaves on your plants, if it doesnt repel the cutworms then the poison in the tomatoe should kill them off. Hope that helps.

Well, the carnage has continued, although there is not much left to chew on. I've been checking every night, sometimes twice a night. I've found out that sow bugs are much more active around dusk and early night...but still no evidence that they are doing the damage, I haven't found any more up on a plant. And I'm slowly but surely depopulating them from my garden boxes. This evil being finally got to the squash and the best plant now has a skeleton of 8 stems with little diomond shaped tufts of leftover leaves at the end of each stem. But I have not seen anything on the plants and I've been checking for 6 nights now. The damage seems to be done after I look and since many times I've looked at 2-3am I'm beginning to think it's happening in the morning when I've asleep. That leads me to suspect a bird.

But a bird can't climb out on the stems of a squash plant, and they won't support it (unless it's a tiny bird). And the squash leaves were 5-8 inches above the ground, not to mention the bean leaves as much as 12-18 inches up. So a tiny bird couldn't get to the squash leaves unless it can hover and eat at the same time...is this possible? Are there nocturnal humming birds that like squash leaves??

I'm trying two more tricks...cayenne pepper powder on the remaining leaves, and some rat traps baited with pumpkin seeds. I just read that birds aren't bothered by the cayenne unless it gets up in the air as a dust. So what can I sprinkle on leaves that would repel a bird? Apparently the aptly named methyl anthranilate is unpalatable to birds and can be sprayed on plants. Has anyone tried this?

Pill Bugs, or Sow Bugs, as a rule are not pests in the garden. They are part of Ma Natures recycling machine and mostly eat dead vegetation, unless so little is left in the garden for them to eat they need to depend on live plants to exist. Sounds more like slug damage to me then anything else.

I agree about sow bugs in general...but I have found them on top of a stem chomping away. I also think they will sometimes chew around the bottom of the stem and kill the seedling that way. And I really really wish it was slugs, they would be easy to get rid of. But I haven't seen one for years, there are no slime trails anywhere, and for the amount of damage done over five large garden boxes plus many container plants, there would have to be a lot of slugs, not just one or two. There would be evidence of slugdom all over the place...and there is none. Plus I've been checking every night and have yet to find anything on a plant except for one or two sowbugs.

Wish I had a video camera hooked up to my computer so I could monitor this 24 hours. There is something making random visits to the gardens and eating at will.