Tomato hornworms can remove a surprising amount of foliage in a short time, but they are often difficult to see because their coloring blends into the plant. A careful evening inspection usually works better than spraying the whole bed.
Look for evidence first
Check for freshly stripped stems, dark droppings on leaves or soil, and branches that look bare overnight. Inspect the upper and inner foliage, where a large green caterpillar may sit along the stem. A flashlight makes the outline and droppings easier to see after sunset.
Remove the caterpillar safely
Wear gloves and lift the hornworm from the plant. Place it in a container for identification or move it away from the vegetable bed according to local gardening practice. Do not crush caterpillars covered with small white cocoons; those are beneficial parasitic wasps developing on the pest.
Check the entire planting
Inspect nearby tomatoes, peppers, and related plants. Remove heavily damaged leaves with clean snips, but keep enough healthy foliage for the plant to photosynthesize. Look under mulch and around supports for additional feeding signs.
Prevent a repeat problem
Keep weeds down around the bed, rotate tomato-family crops, and inspect plants several times a week during peak growth. Avoid broad insecticide sprays that remove beneficial insects and may not be necessary for one or two hand-picked caterpillars.
If damage continues despite inspection, consult a local extension resource about the species and a labeled treatment. Always follow the product label and observe the harvest interval for edible crops.