Pest Identifier

Something is eating your garden, and you would like to know what before you decide what to do. This garden pest identifier works from the evidence you can see: which plants are affected, what the damage looks like, and whether it appears overnight or during the day. It ranks the most likely culprits among the insects and other pests that home vegetable gardeners across the United States meet most often, and suggests how to confirm the diagnosis and control the pest, starting with the gentlest effective options.

How to use the pest identifier

1. Choose the affected plants. Many pests specialize in one plant family, so this narrows the list quickly.
2. Choose the damage. Tiny round holes, large ragged holes, lacy skeletonized leaves, sticky curled leaves, speckling, silvery streaks, winding trails, cut seedlings, wilting vines, damaged fruit, or tunnels in roots.
3. Note when damage appears. Slugs, snails and cutworms feed mostly at night. Japanese beetles and many others feed during the day.
4. Confirm. Go out at dawn or dusk with a flashlight and look under leaves, along stems and on the soil. Seeing the pest itself is the best confirmation.

Reading the damage

Common garden pests

Aphids

Small, soft-bodied insects, green, black, gray or pink, clustered on new growth and leaf undersides. They suck sap, curl leaves and leave sticky honeydew, on which black sooty mold can grow. Natural enemies such as ladybugs, lacewings, hoverflies and tiny parasitic wasps often control them. A strong spray of water knocks them off, and insecticidal soap handles heavier infestations. Heavy nitrogen fertilizing encourages the soft growth they prefer.

Flea beetles

Tiny dark beetles that jump like fleas when disturbed. They chew many small round holes in leaves of eggplant, radishes, arugula, cabbage-family crops, potatoes and tomatoes. Young seedlings suffer most. Floating row cover from planting time keeps them off, and larger transplants usually outgrow the damage.

Cabbage worms and loopers

Velvety green caterpillars that chew large holes in cabbage, broccoli, kale and their relatives, leaving dark green droppings. The adults are the small white butterflies and brownish moths seen fluttering over brassicas. Hand-pick caterpillars, cover plants with row cover to stop egg laying, or use Bt (Bacillus thuringiensis), a biological insecticide that affects caterpillars.

Tomato hornworm

Large green caterpillars, up to several inches long, with a horn at the rear. They are well camouflaged, but their large dark droppings on leaves below are a giveaway. They can strip a tomato plant quickly. Hand-pick them. If you find a hornworm covered in small white cocoons, leave it: those are parasitic wasps, which will emerge and attack more hornworms.

Slugs and snails

Night feeders that chew ragged holes in lettuce, seedlings, strawberries and many other low plants, leaving silvery slime trails. They thrive in damp weather and shady, mulched beds. Hand-pick at dusk, set out traps such as boards or shallow dishes they hide under, and remove debris where they shelter. Baits based on iron phosphate are widely used in vegetable gardens.

Japanese beetles

Metallic green and copper beetles that feed in groups during the day, skeletonizing leaves of beans, roses, grapes, raspberries and many other plants. In the early morning, when they are sluggish, knock them into a container of soapy water. Many extension services advise against pheromone traps in home gardens, because they can attract more beetles to the area than they catch.

Mexican bean beetle

A copper-colored lady beetle relative with black spots, and spiny yellow larvae. Both feed on the undersides of bean leaves, leaving a lacy, skeletonized pattern. Hand-pick adults and larvae, crush yellow egg clusters, and use row cover on young plants.

Colorado potato beetle

Yellow and black striped beetles and plump reddish larvae that strip leaves of potatoes, eggplant and sometimes tomatoes. Hand-pick daily and crush the clusters of orange eggs under leaves. Rotating where you plant potatoes and eggplant each year helps.

Spider mites

Not insects but tiny relatives of spiders, barely visible without a hand lens. They cause fine pale stippling that can turn leaves bronze, and heavy infestations produce fine webbing. They thrive in hot, dry, dusty conditions. Spray leaf undersides with water regularly, and use insecticidal soap or horticultural oil if needed.

Whiteflies

Tiny white, moth-like insects that fly up in a cloud when leaves are disturbed. They feed on leaf undersides of tomatoes, squash, sweet potatoes and many other plants, leaving sticky honeydew. Yellow sticky traps catch adults, and insecticidal soap on leaf undersides reduces numbers.

Thrips

Very small, slender insects that rasp leaf surfaces, leaving silvery streaks and flecks. Onions are a common target. Rinsing plants with water and insecticidal soap can help, and good watering reduces stress.

Leaf miners

Larvae of small flies that feed inside leaves, leaving pale, winding trails or blotches. Spinach, chard and beets are favorites. Remove and destroy affected leaves, and use row cover to keep adults from laying eggs.

Cutworms

Fat, gray or brown caterpillars that hide in the soil by day and cut young plants off at soil level at night. Protect new transplants with a collar of cardboard or a cut-down paper cup pressed into the soil around each stem.

Squash vine borer

A day-flying moth lays eggs at the base of squash and pumpkin vines, and the larvae tunnel into the stems. Vines suddenly wilt, and sawdust-like material appears at the base. Row cover until plants flower prevents egg laying. Some gardeners slit the stem lengthwise to remove the larva, then bury the damaged section so it can root.

Squash bugs

Gray-brown, shield-shaped bugs that suck sap from squash and pumpkins, causing yellow spots and wilting. Look for clusters of bronze eggs on leaf undersides and scrape them off. Boards laid on the soil overnight attract adults, which you can collect in the morning.

Cucumber beetles

Yellow and black striped or spotted beetles that chew leaves and flowers of cucumbers, squash and melons. They can also spread bacterial wilt. Row cover on young plants, removed at flowering for pollination, is the most effective protection.

Root maggots and carrot rust fly

Fly larvae that tunnel into roots of radishes, turnips, onions, carrots and cabbage-family crops. Row cover from the day of sowing is the most reliable prevention.

Control: start gentle

Most home gardeners can manage pests with an approach called integrated pest management. It means identifying the pest correctly, tolerating minor damage, and using the least disruptive method that works.

1. Accept some damage. A few holes rarely affect the harvest. Many pests are controlled by natural enemies if you give them time.
2. Use physical methods first. Hand-picking, water sprays, row cover, collars, traps and barriers are effective and safe.
3. Encourage beneficial insects. Small-flowered plants such as sweet alyssum, dill and cilantro attract predators and parasites. The companion plant finder suggests pairings.
4. Use targeted products if needed. Insecticidal soaps, horticultural oils and Bt are among the lower-impact options for home gardens. Always read and follow the label.
5. Protect pollinators. Avoid spraying open flowers, and if you must spray, do it in the evening when bees are less active.

Preventing pest problems

• Rotate crops so soil-dwelling pests do not build up.
• Use row cover on susceptible crops early in the season.
• Keep plants healthy. Stressed plants attract more pests. Water evenly and grow in good soil.
• Remove crop debris at the end of the season where pests overwinter.
• Mix plantings rather than growing large blocks of one crop.
• Check plants often. A few minutes looking under leaves every couple of days catches problems early.

If you are not sure whether the problem is a pest at all, the plant problem identifier covers watering, disease and nutrient problems too.

Beneficial insects to welcome

Not every insect in the garden is a problem. Many are predators or parasites that keep pests in check, and learning to recognize them saves you from killing your allies.

• Ladybugs and their larvae. The larvae look like tiny, spiky alligators and eat large numbers of aphids.
• Lacewings. Delicate green adults with lacy wings. Their larvae are voracious aphid predators.
• Hoverflies. Small flies that look like bees and hover over flowers. Their larvae eat aphids.
• Parasitic wasps. Tiny, harmless to people, and very effective against aphids and caterpillars. The white cocoons on parasitized hornworms belong to one of them.
• Ground beetles. Dark, fast-moving beetles that hunt slugs, cutworms and other soil pests at night.
• Spiders. General predators that catch many garden insects.

Broad-spectrum insecticides kill these helpers along with pests, which can make pest problems worse over time. Small-flowered plants, a little tolerance for minor damage, and targeted controls keep their populations strong.

Larger pests: animals in the garden

Sometimes the culprit is not an insect at all. Clean bites through stems, whole plants vanishing overnight, dug-up soil and half-eaten fruit often point to animals.

• Deer browse leaves and tender tips, leaving ragged edges, often well above the ground. Tall fencing is the most reliable protection; deer can jump surprisingly high.
• Rabbits leave clean, angled cuts on low plants and seedlings. A fence of small-mesh wire about 2 feet high, with the bottom buried a few inches, usually keeps them out.
• Groundhogs eat large amounts and can climb and dig. Fencing needs to be buried or bent outward at the base and loose at the top so it is hard to climb.
• Birds peck ripening fruit and pull up seedlings. Netting over crops and berries is the simplest fix.
• Squirrels and chipmunks dig in beds and take ripening fruit. Netting, cages and harvesting promptly help.

Using row cover well

Lightweight floating row cover is one of the most effective pest controls available to home gardeners, and it uses no chemicals at all. It is a thin, translucent fabric that lets light, air and water through while keeping insects off. For the best results, put it on at planting time, before pests find the crop. Support it on wire hoops or lay it loosely over plants with enough slack for growth, and seal the edges with soil, boards or pins so insects cannot crawl underneath. Crops that need insect pollination, such as squash, cucumbers and melons, should be uncovered once they start to flower. Leafy crops, root crops and brassicas can stay covered for most of their lives.

Frequently asked questions