The most common pests that damage tomato plants are flea beetles, hornworms and stinkbugs. The sizes and locations of the holes provide helpful clues as to which pests are present.
Flea beetles chew small holes in the leaves, and although the beetles usually don't damage the fruit, the shredded leaves sometimes invite disease. The beetles can be killed with insecticide.
Hornworms are a type of caterpillar, and they can eat all of a plant's leaves and developing fruit. Hornworms should be picked off individually.
Stinkbugs leave tiny holes on unripe tomatoes, causing internal damage. Consistent weed control prevents stinkbug infestation.