What eats tomato plants and how to spot the damage

Several insects, mites, and animals eat tomato plants, and each one leaves a different pattern of damage. Hornworms chew large, ragged holes in leaves and can strip a plant bare in days. Aphids cluster on stems and the undersides of leaves, leaving them yellowed and sticky. Spider mites create a fine webbing and cause leaves to look speckled and pale. Whiteflies fly up in a cloud when you brush the plant and leave yellowing leaves behind. Larger animals like deer, rabbits, and groundhogs bite off entire stems or eat fruit directly from the vine.

The damage pattern tells you what you are dealing with. If you see large, irregular holes with dark droppings nearby, look for hornworms on the stems and undersides of leaves—they are green and can be four inches long. If leaves are curling, yellowing, or sticky to the touch, check the undersides for clusters of tiny soft-bodied insects. If the plant looks dusty and weak but you see no insects, suspect spider mites. If you find small white insects that scatter when disturbed, whiteflies are the culprit.

Key Takeaways

  • Hornworms are large green caterpillars that eat holes in leaves and fruit; they are easiest to spot by looking for dark droppings on the ground below damaged areas.
  • Aphids, spider mites, and whiteflies cluster on the undersides of leaves and cause yellowing, wilting, or sticky residue without eating visible holes.
  • Deer, rabbits, and groundhogs bite off entire stems or eat ripe fruit; fencing or netting is the most reliable way to stop them.
  • Identifying which pest is present before treating prevents wasting time on the wrong solution.
  • Early detection—checking plants two to three times a week—stops most infestations before they cause serious damage.

Hornworms and other large caterpillars

Tomato hornworms are the most destructive caterpillar on tomato plants. They are bright green, up to four inches long, and have white stripes running down their sides. A single hornworm can eat an entire leaf in one sitting and will move on to fruit if leaves run out. Look for dark green or black droppings on the ground or on leaves below the damage—that is the easiest way to find them, since the caterpillars blend in with the plant.

Other caterpillars that eat tomatoes include armyworms (smaller, striped, and often found in groups) and cutworms (which chew seedlings at soil level and hide in the soil during the day). Hornworms are solitary, so you may only have one or two on a plant. Armyworms often arrive in clusters and can strip a plant faster. Check the plant in early morning or late evening when caterpillars are most active, and look on the undersides of leaves and along the main stem.

Aphids, spider mites, and whiteflies

Aphids are tiny soft-bodied insects, usually green or black, that cluster on new growth and the undersides of leaves. They pierce the plant and suck out sap, which causes leaves to curl, yellow, and eventually drop. Aphids also leave behind a sticky residue called honeydew, which can turn black if mold grows on it. A light infestation may not kill the plant, but a heavy one will stunt growth and reduce fruit production.

Spider mites are even smaller than aphids—so small you may not see them without a magnifying glass—but they create a fine webbing on the undersides of leaves. Infested leaves look speckled or bleached and may turn brown and drop. Spider mites thrive in hot, dry conditions and can multiply very quickly. Whiteflies are tiny white insects that fly up in a cloud when you touch the plant. Like aphids, they suck sap and leave sticky residue, causing yellowing and wilting.

All three of these pests weaken the plant over time rather than eating visible holes. If you catch them early, a strong spray of water from the hose can knock many off the plant. For heavier infestations, insecticidal soap or neem oil can slow them down, though you may need to spray every seven to ten days.

Deer, rabbits, and groundhogs

Larger animals cause different damage than insects. Deer bite off entire stems and leaves, leaving a clean, angled cut. They often eat the fruit as it ripens and can devastate a garden overnight. Rabbits also bite off stems cleanly but usually target lower leaves and seedlings. Groundhogs eat leaves and fruit and may dig under the plant or nearby soil. All three leave behind droppings and often return to the same plants night after night.

Fencing is the most reliable defense. For deer, a fence should be at least six feet tall and angled outward at the top, since they can jump high and climb. For rabbits and groundhogs, a fence two to three feet tall with the bottom buried six inches underground stops most animals. Electric fencing also works well for all three. If fencing is not an option, row covers or netting over individual plants can protect them, though you will need to remove the cover when the plant flowers so bees can pollinate.

How to check your plants regularly

The best defense against any pest is catching it early. Set a routine to check your tomato plants two to three times a week, especially during warm months when insects multiply fastest. Look at the top and undersides of leaves, along the stems, and on the fruit itself. Gently turn a leaf over and look for clusters of insects, webbing, or sticky residue. If you see damage, look for the pest itself before deciding how to treat it.

Early morning or late evening is the best time to check, since many pests hide during the heat of the day. Keep a notebook or phone photo record of what you find—this helps you track whether a treatment is working and whether the same pest returns year after year. If you find only one or two hornworms or a light aphid infestation, hand-picking or a water spray may be all you need.

When to treat and when to leave it alone

Not every pest requires treatment. A few aphids or a single hornworm on a healthy plant may not cause enough damage to justify spraying. If the plant is producing fruit and the damage is only on older leaves, the plant can often outgrow the problem. However, if you see rapid damage, multiple pests, or damage spreading to new growth, treatment becomes worthwhile.

Before spraying anything, identify the pest correctly. A treatment that works on hornworms will not help with spider mites, and vice versa. If you are unsure, take a photo or a sample leaf to your local extension office—they can identify the pest and recommend the best treatment for your situation. Many organic options exist, including hand-picking, water sprays, insecticidal soap, neem oil, and spinosad, each suited to different pests and situations.

Frequently Asked Questions

How do I know if it is a hornworm or another caterpillar?

Hornworms are large (three to four inches), bright green with white stripes, and solitary. Armyworms are smaller, striped, and often found in groups. Look for dark droppings on the ground below the damage—that is the easiest way to confirm a hornworm. Cutworms hide in soil during the day and chew seedlings at ground level.

Can I use the same spray for aphids and spider mites?

No. Insecticidal soap works well on aphids and whiteflies but is less effective on spider mites. Neem oil works on both but may need more frequent applications for spider mites. If you are unsure which pest you have, identify it first before buying a treatment.

Will netting hurt my tomato plant?

Row covers and netting protect plants from insects and animals but must be removed once the plant flowers so bees can pollinate. If left on too long, the plant may overheat or become too crowded. Use netting mainly on seedlings or early in the season before flowering.

What if I see damage but no insects?

Check the undersides of leaves carefully—many pests hide there. If you still find nothing, the damage may be from spider mites (which are too small to see easily), cutworms (which hide in soil), or an animal that visited at night. Look for droppings or tracks to narrow it down.

Is it safe to eat tomatoes if I have sprayed them?

Follow the label instructions on any spray you use, including how many days to wait before harvesting. Organic sprays like insecticidal soap and neem oil typically have short waiting periods—often three to seven days. Wash fruit before eating regardless of what was sprayed.