What is Topping My Tomatoes?

I had a similar problem. For the previous 3 years I could never grow peas. As soon as their height would reach the fence (about 4inches) rabbits would nibble them down to the ground. I never minded them (it looked like the entire bunny family, Papa, Mama, and their kids) grazing through my lettuces or spinach. In fact, what a sweet site to watch. I felt blessed and honored. But when it came to the peas, I didn't like them so much. This year I was going to give it one more try, only I was going to be on the defense and be prepared early. I bought a huge container of cayenne pepper. As soon as my peas sprouted out of the ground I sprinkled the pepper on and around each plant. If I watered or it rained I reapplied. For the first time in all the years I've been gardening I had beautiful, lush, well producing pea plants.

It also could be a groundhog. They have been eating all my tomatoes too. They nibble on tops and continue till there is only a stem with no leaves on it. I'm still trying to find out how to stop them.

It is almost certainly a tomato hornworm or a tobacco hornworm. They are closely related and behave exactly as you describe. They grow to be huge, long and fat. They are the same color green as the plant and are often very hard to see. They feed most often at night and early morning and if you can't find them, they might have gone under the loose soil in the heat of the day. Look for telltale little black poop on lower leaves to give a hint of where they might be. They poop a lot. Find those little suckers, or they can eat your entire tomato crop before you know it if you have a lot of them.

I had a similar problem last year and I found a horned worm on one plant. It will eat the tops of your plant, I guess it likes the new growth. The are big, but hard to see, they blend in. That might be your problem.