|by that I mean the scissor-like jawed, big green,cocoon-like creature that will eat all the leaves on my tomato plants before I can see them!
How can they be prevented in the first place? they are growing so vigorously I'd hate to see them mowed down!!
|I think you mean tomato hornworms, a life stage of the sphinx moth. Luckily, just because you had a problem last year does not necessarily mean it will happen again this year. These are large enough to seen and removed by hand. They are the larvae of a moth so not easily prevented, but you could treat the plants with Bt (the active ingredient in Dipel for example) if you want to try. Read and follow the label directions. Here is more information you may find interesting.
Enjoy your tomatoes this summer!