Damage that severe - and that widespread - would most likely be deer or a woodchuck. Both will leave bare stems. If your fence is too high for deer to jump over (at least 6 feet high) then I would look for a hole under your fence. I am battling a woodchuck right now; in the past, live trapping has been effective. Which reminds me to go check my trap... I had to reset it yesterday when I caught a possum.

Jean, Thanks, that's it. The first thing I thought when I saw them is they look like a turtle. When I searched "turtle insect tomatoes" on Google earlier and saw tortoise beetles the pictures didn't look enough like this one. I did more searches and found a picture of the exact kind after I read your post. Will BTK kill them if they become a problem? In past years they were more of a problem on pepper plants and not tomato plants but I don't have any pepper plants this year. Thanks, Don

Groundhog damage sounds like to me, if no deer around. Squirrels usually just go for the fruit. Any sign of rat droppings? They will eat most of the plant. If you are living in town the choices are usually narrowed than for those of us out in the country. Dave

Thanks for all the tips. I live in Pleasanton, CA. Deer is unlikely since the plant is in the patio and the door is mostly locked! It could be one of the caterpillars or slugs but I don't see any activity during daytime. I have inspected the plant over and over.. Whatever it is, seems very hard to detect. For my tomato plants, I did see hornworms last time but with hornworms I would see half eaten leaves and lots of black spots on the ground. Not this time. Also, this time the leaves seem to have been eaten completely! Not a single half eaten leaf.. It is almost as if someone has plucked the leaves..