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I have sea lavender and verbena getting decimated by the worms. What are they? What will kill these destructive critters? Thank you in advance.

That looks like a cutworm. Does it coil into a circle if you poke at it? If they are cutworms, they climb up and feed at night and climb down to hide in litter/under leaves, mulch, or dug in under the soil. It helps to shallowly rake around under the plants to unearth them as you seem to have done in the photo, and get rid of them. You may also find brown pupae in the ground.

What part of the plants are they eating? Since they are moth caterpillars, Bt (thuricide, dipel) should work, but be very careful not to spray the flowers (and upper foliage) which are butterfly magnets since this pesticide will infect them and could potentially transmit the bacteria to their caterpillars.

Yes they coil up if poked or prodded.they at the leaves of the plants. They've almost wiped out the verbena.!

Yep cutworms. Bt is a species of bacteria that disrupts digestion and kills butterfly and moth caterpillars when eaten.

You would be surprised at how much damage one single cutworm caterpillar can inflict. Since you found your culprit just squish it. Look around in the early morning hours for more. The best time is when the sun is up but dew is still on the ground.