There is one caterpillar, the horned worm caterpillar, that has the ability to completely destroy your tomato plants. It is also known as the tomato horn worm. This green caterpillar must be killed as soon as it is spotted so that no further damage occurs to your tomato plants.
Lift up the leaves of your tomato plants and look for tiny caterpillar eggs. You can remove these eggs by hand and burn them. This is an easy way to destroy the caterpillar before it has a chance to destroy your tomato plant.
Set a few bird houses near your crop of tomatoes. Birds are natural predators to the caterpillar and will kill and eat any caterpillars they see.
Plant sweet alyssum, fennel, dill, or spearmint next to your tomato plants. Tiny parasitic wasps that are attracted to these plants will see the caterpillars and lay their eggs on them. When the eggs hatch, the larvae eat right through the caterpillar and kill it.
Make your own insecticidal spray. Fill a spray bottle with a water and add dish soap. Mix the ingredients together and spray your tomato plants with it. This solution will not hurt your tomato plants at all. It will, however, kill the horned worm caterpillar.