Control Hornworms With Barriers
Unless plants are trained to a trellis, you can easily protect them from tomato hornworms with garden fleece , also called floating row cover. This lightweight spun-bonded fabric allows sun, air, and rain to get through while keeping out the moths and their eggs as long as the entire plant is covered. Cover transplants or a newly seeded area with the material immediately; lay it directly on the plants or over a framework. Seal all the edges to the ground, and leave the barrier on at least until blossoms appear, after which it will need to be removed to allow insects to reach the flowers to pollinate them. You can leave the row cover over the plants all season if you are growing plants that do not need external pollination, such as “parthenocarpic” cucumber varieties. (Such plants are able to set fruit without being pollinated by bees.) Provide lots of extra material so when the plants grow larger they don't strain against the covering.
Coffee Can Trick
If garden fleece is impractical in your situation, you can still protect individual transplants against hornworms with small screened enclosures . Cut out both ends of a coffee can, cover one end with a square of fleece fabric held in place with a stout rubber band, and set the other end into the ground around the plant.
Control Hornworms By Hand Picking
Hand picking is the easiest way to control most populations of tomato hornworms and can keep them from getting out of hand if you catch the infestation right away. To spot the caterpillars before they have reached full size, look for dark-colored droppings on the leaves and spray the plants with water. The caterpillars will thrash about and give away their location. Drop them into a can of water with a bit of insecticidal soap in it.
A “Dilly” of a Decoy Trick
Try planting a trap crop. such as some dill, around your tomatoes, eggplants and peppers and keep an eye out for early-arriving hornworms on the dill.
Important Note: If your garden is healthy, you may find small, white, elliptical braconid wasp coccoons attached to the hornworm's back. Don’t kill any caterpillars bearing these coccoons. Just move the hornworms away from your crops to allow these parasitic wasps to mature.