Those sure look like webworms (also called "bagworms" because of the white bag-like nests seen around the joints of stems and leaves). Rare to see them on tomatoes but if the area is badly infested with them it is possible. Cool wet weather also encourages them.

You need an insecticide called Bacillus Thuringiensis (BT) which comes in dust or liquid. Liquid bacillus best in this case I think for full coverage. Try to spray quickly or they will kill the plants.

Dave

PS: you can find a great deal of info on webworms on the web (no pun intended) and learning how to recognize the nests and about fall controls for them will really help prevent spring problems.