Bugs that attack tomato plants are sometimes never seen, but you can see the damage they leave behind. You first need to identify the bug on your tomato plant before you can determine the best approach to eradicate it. In some cases, chemicals are needed to stop the pests. Read the label carefully and follow the directions precisely to avoid harm to humans, pets and beneficial insects, like honey bees. The following bugs that have been found to attack tomato plants are common to the continental United States.
What to do. Nature may take care of the problem for you. The extremely tiny, trichogramma wasp will eat the eggs of the cabbage looper, stopping their reproductive cycle. If that fails use sabadilla, which is a chemical contained in products like Natural Guard, to kill the bugs (see Botanical Insecticides for details).
Colorado Potato Beetle
What to do. Prevent the beetle from reaching the plant's leaves by applying 6 to 12 inches of mulch is one option. A chemical approach is to use rotenone (see Botanical Insecticides link under Sources below for details). Check with your county extension office for other suggestions if this pest becomes invasive.
What to do. Beneficial garden bugs may control the problem by eating the larvae. Locate and pick off the armyworm. Be sure to destroy armyworm.
What to do. The trichogramma wasp may work, in time, to prevent more hornworms. The better approach is to pick the hornworm off the plant and dispose of it.
The common brownish-black field cricket, about 1 inch long, will chew on the leaves and flowers of tomato plants.
What to do. Let the birds and toads visit your garden to dine on the crickets.