6 Common Pests That Ruin Tomato Plants—Plus, Tips for Preventing and Treating Each

Many gardeners know how rewarding it is to grow and harvest tomatoes. But just as deflating is seeing your hard work go to waste due to bugs dining on your fruits. Anyone with experience growing this beloved edible plant will tell you it comes with plenty of common garden pests.

The good news is that, in many cases, you can prevent or treat these pests before they become a problem. Here, we have rounded up the most common tomato pests and enlisted the help of a certified master gardener to share her tips on how to prevent and treat them.

Colorado Potato Beetles

Colorado potato beetle (Leptinotarsa decemlineata) is a potato pest across North America, but also feeds on other crops, including tomatoes. They appear on young tomato plants in spring. "They start with small holes and may remove all leaf tissue if left alone,” says Mary Jane Duford, certified master gardener at Home for the Harvest. They can also feed on peppers, eggplants, and nightshade weeds.

• Prevention: To prevent infestations, remove weeds in the nightshade family from your garden, which can attract Colorado potato beetles. Plant dill, alyssum, and yarrow to attract beneficial bugs that eat harmful insects.
• Treatment: Once your tomatoes are infested with these beetles, you only have a few options: pick beetles, larvae, and eggs by hand and then drop them into soapy water to kill them. You can also wipe the foliage with insecticidal soap sprays. “Stopping this first generation early can reduce future outbreaks," says Duford.

Aphids

Aphids feed on tomato plants by sucking sap from leaves and stems, causing leaves to curl, turn yellow, or stop growing.

• Prevention: Prevent aphids from attacking your tomatoes by introducing ladybugs and lacewings to your garden, as these insects eat aphids.
• Treatment: Spray your tomato plants with a sharp stream of water a few days in a row to dislodge the insects, says Duford. "If populations remain, spray the plant with insecticidal soap or neem oil." Remove the stems that are heavily infested. 

Slugs and Snails

Slugs and snails feed at night on damp areas of your tomato plant, chewing holes in leaves and fruit. Both also leave behind shiny slime trails on your plants. Luckily, the treatment for slugs and snails is the same, says Duford.

• Prevention: Prevent snails and slugs by watering your plants in the morning so the soil dries before nightfall. That way, these pests will be less likely to venture into your garden at night. "Also, pull mulch away from plant stems to reduce shelter for these pests," Duford says.
• Treatment: Duford recommends handpicking snails and slugs off your tomato plants at night, which is when they tend to do their damage. "You can even lay damp boards or cardboard on the ground nearby to attract them and then collect and discard these each morning," she says. 

Flea Beetles

Adult flea beetles chew tiny round holes in tomato leaves, giving them a lacy appearance. Meanwhile, the larvae live underground and feed on tomato roots. "Tomato seedlings are most at risk from flea beetle damage," says Duford. "While larger plants can survive light feeding."

• Prevention: To prevent flea beetle infestations, remove potatoes and nightshade weeds from your garden to lower beetle numbers and minimize attracting new populations. "Also, rotate your crops, especially tomato or potato family plants." Additionally, mulching the soil will help block beetles from reaching your plants.
• Treatment: If flea beetles have infested your tomato plants, using a pesticide may the best course of action. Use a product designed to treat just this pest. Also, check how many days you need to wait to harvest your crop after applying the pesticide.

Whiteflies

Whiteflies live on the undersides of plant leaves and suck on the juices. Luckily, they are most common in greenhouses or indoor setups. Still, they can severely harm your tomato plants, says Duford.

• Prevention: Space plants to improve airflow, removing any warm spots where the bugs will collect. "Avoid over-fertilizing, which can create weak, tender growth that attracts these pests."
• Treatment: Wash plants with water and spray them with insecticidal soap if a whitefly infestation occurs. Apply the soap as often as the label indicates. 

Tomato Hornworms

Tomato hornworms are large green caterpillars that grow up to 4 inches long. They have white V-shaped marks and a pointed black horn—hence their name. Hornworms chew holes in tomato leaves and fruit, and they can remove most of the plant’s foliage in a short time, says Duford.

• Prevention: Grow companion pest-repelling plants with tomatoes to prevent tomato hornworms, says Duford. Till your garden soil in fall or spring to kill overwintering pupae, she adds.
• Treatment: Check your tomato plants often during summer, when these pests are out looking for a meal. "Remove hornworms by hand and destroy or relocate them far from your garden," says Duford.