for the last few days we couldn't figure out why our tallest dahlia has been slowly going limp the leaves are flawless and we didn't see anything obvious. thought maybe it was a weather related issue...? well... I went on slug patrol this morning with my trusty flashlight and I soon found out the cause of all the limpness!! they (slugs, earwigs, snails, cutworms...?) chewed the main stem off right at the base about 1/2 inch below the surface of the soil!! I only noticed it because the entire plant was bent over. I had to scrape away some of the mulch just to get a better look. the entire area where it was chewed was all black. luckily, theres another shoot coming up from the bulb just to the side of this one. we only planted 5 dahlias this year, so this really set us back.

That definitely sounds like a cutworm!

Yes, much more like a cutworm than anything else you named, Jason.

There is an earwig/slug control (I think the label includes cutworms); it's good for clematises as well since the slugs and earwigs tend to devour clematises and leave them looking terrible.