The tomato horn worm is the biggest pest your tomato plants will have. You will know one has moved onto one of your plants when you notice leaves being eaten off of the stems. They will also eat into the side of your tomatoes. Tomato horn worms have large appetites. It will not take too many days before you will see the damage they create. Once you see the signs, start looking very carefully on the bottom of each leaf stem until you spot the worm.
After you hand remove the horn worm, kill it by cutting it in half. You can smash it; just beware that it will make a bit of a mess this way.
If you find a worm that has white sacks hanging onto its back, do NOT remove it! Leave it right where it is on your tomato plant. The white sacks are the eggs of the parasitic wasp, one of nature's beneficial insects. These eggs survive by sucking the life out of the horn worm. Once these eggs hatch, the wasp will go out looking for more horn worms to lay eggs into and kill.