What Is Eating My Tomato Plant Stems

If you’re noticing damage to your tomato plants, you’re likely asking yourself, what is eating my tomato plant stems? Holes or gouges in tomato plant stems point to a handful of likely garden culprits. Identifying the pest is the first critical step to saving your crop. This guide will help you diagnose the problem and provide effective, practical solutions.

Stem damage can range from small holes to large, chewed channels. Some pests bore inside the stem, while others feed on the outer surface. The time of day you see the damage can also be a clue. Let’s look at the common offenders and how to spot them.

Several insects and animals find tomato stems appealing. The most common pests that target stems include tomato hornworms, cutworms, stem borers, and certain types of beetles. Even rodents like voles or rabbits can cause this kind of damage. Careful observation of the signs will narrow down the list.

Identifying Tomato Hornworm Damage

Tomato hornworms are large, green caterpillars that can strip a plant quickly. They are often difficult to spot because their color blends with the foliage. The damage they cause is distinctive.

Look for large, irregular holes in leaves and stems.
Check for dark green or black droppings on leaves below the damage.
Stems may have large sections of bark chewed away, sometimes girdling the plant.
The caterpillars themselves can be up to 4 inches long with a distinctive “horn” on their rear.

Cutworms And Their Stem Attacks

Cutworms are nocturnal caterpillars that feed at night. They are notorious for chewing through young tomato stems at the soil line, effectively cutting the plant down. They hide in the soil during the day.

Plants are found severed at the base, often lying on the ground.
Look for chew marks near the soil surface on surviving plants.
Small, curled gray or brown caterpillars may be found just beneath the soil surface nearby.

Preventing Cutworm Damage

Prevention is key with cutworms. Simple barriers can be very effective.

Place cardboard collars or aluminum foil around the base of each seedling at transplant time.
Push the collar about an inch into the soil and leave 3 inches above.
Keep the area free of weeds and debris where cutworms can hide.

Tomato Fruitworm And Stem Borer Issues

While the tomato fruitworm (also called corn earworm) is known for eating fruit, it will also bore into stems. Similarly, the stalk borer is a pest that tunnels into stems, causing wilting.

Signs of borer activity include:

Small holes in stems, often near leaf joints or the base.
Sawdust-like frass (insect waste) around the entry hole.
Sudden wilting of a branch or the entire plant despite adequate water.
If you slit open a wilted stem, you may find the creamy-colored caterpillar inside.

Beetles That Chew On Stems

Certain beetles, like the Colorado potato beetle or flea beetles, may chew on tomato stems, especially on young, tender plants. Their damage is usually smaller and more scattered than hornworm damage.

Flea beetles create many tiny, shotgun-like holes.
Colorado potato beetle larvae and adults can chew larger pits and grooves.
Look for the beetles themselves on the undersides of leaves or on stems.

How to Inspect Your Tomato Plants for Pests

Regular inspection is your best defence. Catching pests early makes control much easier. Follow this step-by-step inspection routine.

Conducting A Thorough Daytime Check

Check your plants during the day, preferably in the morning. Bring a flashlight to peer under leaves and into dense foliage.

Start at the top of the plant and work your way down.
Examine the undersides of leaves carefully, as many pests hide there.
Look along the stems for holes, sawdust, or the pests themselves.
Check the soil line and the base of the stem for cutworm damage or hiding insects.

Performing A Nighttime Inspection

Since many pests are active after dark, a nighttime check with a flashlight can reveal culprits you’ll never see during the day. This is especially useful for cutworms, slugs, and hornworms, which sometimes feed more actively in the cool of the evening.

Be gentle to avoid disturbing the plant to much. Quietly approach and shine your light along stems and leaves.

Organic and Natural Control Methods

Before reaching for harsh chemicals, consider these effective organic controls. They protect your garden’s ecosystem and are safe for you and beneficial insects.

Handpicking Pests

For larger pests like hornworms, handpicking is very effective. It requires diligence but is immediate.

Drop hornworms or beetles into a bucket of soapy water.
For borers, you can sometimes slit the stem carefully with a razor blade to remove the caterpillar, then bury the wounded stem section in soil to encourage new roots.
Check plants daily when pests are active.

Using Biological Controls

Encourage or introduce natural predators. Birds, parasitic wasps, and predatory insects are you’re allies.

Plant nectar-rich flowers like marigolds, dill, and yarrow to attract beneficial wasps that parasitize caterpillars.
If you see a hornworm covered in white, rice-like cocoons, leave it. Those are the pupae of parasitic wasps that will create more helpers for your garden.
Consider applying Bacillus thuringiensis (Bt), a natural soil bacteria that is toxic to caterpillars when ingested but harmless to other wildlife.

Applying Diatomaceous Earth And Other Barriers

Diatomaceous earth (DE) is a fine powder made from fossilized algae. It works by physically damaging the exoskeletons of insects. It loses effectiveness when wet, so reapply after rain or dew.

Other physical barriers include:

Copper tape around containers to deter slugs and snails.
Floating row covers to prevent moths from laying eggs on plants.
Collars, as mentioned, for cutworms.

When to Consider Insecticidal Solutions

If organic methods are not enough and damage is severe, you may need to use an insecticide. Always choose the least toxic option that targets your specific pest.

Selecting The Right Insecticidal Soap Or Oil

Insecticidal soaps and horticultural oils (like neem oil) work by suffocating soft-bodied insects such as aphids or young caterpillars. They have little residual effect and are low-impact.

Ensure you cover the pest directly, as the spray must contact the insect to work.
Apply in the early morning or late evening to avoid harming pollinators and to prevent leaf burn in hot sun.
Test on a small part of the plant first to check for phytotoxicity.

Using Botanical Insecticides Like Pyrethrin

Derived from chrysanthemum flowers, pyrethrins are fast-acting, broad-spectrum insecticides that break down quickly. They are more toxic to beneficial insects, so use them sparingly and precisely.

Only spray plants that are infested.
Apply directly to the pests you see, avoiding open flowers where bees may visit.
Use as a last resort when other methods have failed.

Repairing Damaged Tomato Stems

Even heavily damaged plants can often be saved. Tomato plants are remarkably resilient and can produce new roots from their stems.

Mending Girdled Or Partially Cut Stems

If a pest has chewed a ring around the stem (girdling), it can block the flow of water and nutrients. You can try to bridge the gap.

One method is to carefully wrap the damaged section with grafting tape or even electrical tape. This can sometimes hold the plant together long enough for it to callus over and heal. Another method is to bury the damaged section. If the damage is low on the plant, you can mound soil around it to encourage rooting above the injury.

Using Support And Splints

For stems that are broken or severely weakened, you can create a splint.

Gently straighten the stem.
Place a small stick or pencil along the damaged section as a brace.
Use soft plant tape or cloth strips to secure the stem to the splint. Don’t tie it to tight.
Provide extra support to the plant with a stake or cage to prevent further stress.

Preventing Future Pest Problems

A healthy garden is the best prevention. Pests often target stressed or weak plants. Focus on building a robust growing environment.

Crop Rotation And Garden Hygiene

Many pests overwinter in soil or plant debris. Disrupt their life cycle with good practices.

Rotate your tomato plants to a different area of the garden each year.
At the end of the season, remove and dispose of all tomato plant debris—do not compost it if you had pest issues.
Till the soil in fall to expose overwintering pupae to cold weather and birds.

Companion Planting For Protection

Some plants can help repel pests or attract their predators. While not a foolproof solution, companion planting adds diversity and resilience.

Basil is famously planted with tomatoes and may help repel some insects.
Borage can deter tomato hornworms.
Garlic and onions may help repel aphids and other sap-suckers.

FAQ: Common Questions About Tomato Stem Pests

What Animal Is Eating My Tomato Stems At Night?

If the damage is large and the stems are cleanly cut or gnawed, suspect animals. Voles, rabbits, or even deer (though they usually go for leaves) can chew stems. Look for tracks or droppings. Fencing or hardware cloth cylinders around the base of plants can deter animals.

Why Are There Holes In My Tomato Stems?

Small, round holes are often the entry points for stem borers like the tomato fruitworm. Larger, ragged holes or gouges are typical of hornworms or beetles. The size and shape of the hole is a major clue to the pest’s identity.

Can A Tomato Plant Recover From Stem Damage?

Yes, tomato plants can recover from significant stem damage if the damage isn’t a complete girdle and the plant is otherwise healthy. Using the repair methods like burying the stem or providing support can give the plant a chance to heal and produce new roots.

How Do I Stop Caterpillars From Eating My Plants?

For caterpillars like hornworms and cutworms, a multi-pronged approach works best. Combine daily handpicking, encouraging natural predators, and applying Bt if the infestation is severe. Keeping your garden clean of debris removes hiding spots.

Are Holes In Stems Always Caused By Pests?

Not always. Sometimes, small holes or cracks can be caused by physical damage, like from staking or weather. However, if you see frass (insect waste) around the hole, or if the hole looks chewed, an insect is the likely cause. Splits from rapid growth are usually clean and vertical, not round or gnawed.