It sounds like a cut worm to me. Dig a little around the base of the victim plants and see if you can find it. They will go higher than a toothpick so use little sticks or something a little bigger. I don't spray much but maybe a little Dipel dust would help.

On further thought by the time Dipel works your seedling is cut down. Use sticks or a paper collar.

Here is a link that might be useful: Dipel thread from long ago

Stick the cut-off plant back in the ground and keep it watered. Tomatoes are very good at putting out new roots. I have done this, and while the plant is smaller at first, it catches up with the others and produces well.

Another victim last night. At this rate the entire raised bed is going to be destroyed. I dug around the severed plant and found several of these. Could they be responsible? The stem was just chewed straight through a little below the soil line.

Lane,

I think you have found the culprit! Because of the way he is curled and drawn in, I can't tell for sure if I see feet under him, which would make him a caterpillar and probably a "black" cutworm. If he has no feet, he's a grub and may or may not be the responsible critter.

Betsy

Here is a link that might be useful: Cutworms in Home Gardens (U of Mn)

Sprinkle something there to kill them. That doesn't look like a cutworm to me, but I think a cut worm is doing it.

Here is a link that might be useful: cutworms

The image is a beetle larva -- a grub. It feeds underground. Depending upon the kind, it may or may not be a garden pest. But one thing I'm certain -- It didn't damage the top of the plant

It's definitely the base of the plant right at the root line that is getting severed. And whatever pest it is has no problem mowing through a stem as big around as my finger.

I'm dreading waking up tomorrow morning to find another plant gone. Several months of work down the drain in a night.

Could a vole be responsible? Digging around tonight I thought I felt a few hollowed out tunnels in the dirt...

If I don't put sticks around my tomato plants, cut worms will get some of them. It is not the end of the world; just put something there to protect the stem. It is a very common problem.

I'm definitely finding tunnels several inches below the surface with a diameter of an inch or maybe a little less. Last night the stem of a Kosovo plant was cut about 3" below the soil line. At this point I don't know what to do as sticks next to the stems don't help. I had foil wrapped around them too, but not down to that depth. I'm thinking that this has to be some other creature because it's leaving these sizable tunnels behind that I can trace with my fingers when I dig down into the soil.

I'm trying to dig up the remaining plants in that bed and put them in pots. It's a pity as the plants are growing great and setting fruit. Leaving them there seems to be a death sentence though. Half have been wiped out in a week.