Garden Pests: Identify Them, Outsmart Them

What it looks like

Metallic copper-and-green beetles, about a half-inch long, feeding in groups on the tops of leaves in midsummer. They favor roses, beans, grapes, and many ornamentals, and they are easiest to spot clustered on warm mornings.

The damage

Leaves skeletonized to a lace of veins — the green tissue eaten away between them — plus chewed flowers and the beetles themselves out in the open.

The move

Hand-pick into soapy water early and often, in the cool of the morning when they are sluggish, and skip the pheromone traps — they pull in more beetles than they catch. Row-cover high-value plants through the few peak weeks. A healthy, well-watered plant shrugs off damage that looks worse than it is.

What it looks like

Velvety green caterpillars on cabbage, broccoli, kale, and their kin — the imported cabbageworm creeps along plump and fuzzy, the looper humps its back as it moves. Both are so well camouflaged you usually spot the damage first.

The damage

Ragged holes chewed through the leaves and into the heads, with crumbly dark-green droppings collecting in the crown of the plant.

The move

Row-cover the bed from transplant on — the white cabbage butterfly cannot lay eggs through it — hand-pick what slips in, and reach for Bt (Bacillus thuringiensis), a targeted biological that hits caterpillars and spares bees and beneficials. Healthy plants outgrow light feeding.

What it looks like

Tiny black or bronze beetles that spring away like fleas when disturbed, working over the leaves of eggplant, radishes, brassicas, and tomatoes. The seedlings take the worst of it.

The damage

A pepper-shot of small round "shot-holes" scattered across young leaves; heavy feeding can stall or kill seedlings outright.

The move

Protect seedlings under row cover until they are big enough to outgrow the damage, keep plants vigorous, and use a trap crop or reflective mulch to throw the beetles off. Mature plants tolerate the holes fine — the only urgency is at the seedling stage.

What it looks like

A rounded beetle with bold yellow-and-black stripes on potatoes, eggplant, and tomatoes, alongside humpbacked brick-red larvae and clusters of bright orange eggs on the leaf undersides — adults, larvae, and eggs often all on the same plant.

The damage

Rapid defoliation — larvae and adults together can strip a potato plant to bare stems — and the orange egg masses tucked under the leaves.

The move

Scout the leaf undersides and crush the orange egg clusters before they hatch — the highest-leverage move you have. Hand-pick adults and larvae, rotate potatoes and eggplant well away from last year’s bed, and mulch deep with straw, which slows the adults walking in. They resist many sprays, so the mechanical moves carry it.

What it looks like

Fat, dull gray-brown caterpillars that curl into a tight C when you disturb them. You rarely catch them in the act — they feed at night and hide in the soil by day.

The damage

A young transplant clipped off clean at the soil line overnight, lying beside its own stump in the morning, as if cut with scissors.

The move

A simple collar around each transplant — a toilet-paper tube or a cardboard ring pushed an inch into the soil — stops them cold. Clear the weedy debris where they shelter, and when a plant goes down, press a finger into the soil around it: the culprit is usually within an inch or two.

What it looks like

A big — up to four-inch — soft green caterpillar with white side-stripes and a single soft horn at the tail, on tomatoes, peppers, and eggplant. Its near-twin the tobacco hornworm is just as common in gardens: the tomato hornworm carries V-shaped white marks and a dark horn, the tobacco hornworm diagonal white stripes and a red horn — both do exactly the same damage, so the move is the same.

The damage

Defoliation from the top down, plus scattered dark pellet-like droppings on the leaves below. Follow the droppings up and you will find the caterpillar — it is invisible until you learn its outline.

The move

Hand-pick at dawn or dusk and drop them in soapy water; a few can clear a plant. Leave any hornworm studded with white rice-like cocoons — those are braconid-wasp pupae, and that wasp is your free, self-renewing control. Turning the soil in fall disrupts the pupae for next year.

What it looks like

You almost never see the culprit — a fat white grub tunneling inside the stem. The adult is a clear-winged moth that looks more like a wasp. What you notice is the plant, not the pest.

The damage

A squash or pumpkin vine that wilts suddenly from midsummer on, with a ragged hole near the base oozing sawdust-like frass, and a hollowed stem when you split it.

The move

Timing is everything: cover young plants until they flower (then lift the cover for pollination), mound soil over the vine at the leaf nodes so it can re-root past a wound, and if a borer is already in, slit the stem lengthwise, remove the grub, and bury the wound. A second, later succession planting is cheap insurance.

What it looks like

Clusters of tiny soft-bodied insects — green, black, gray, or peach — packed onto new growth and leaf undersides. The tells: curled, puckered leaves, a sticky shine on the foliage below, sometimes black sooty mold on that shine, and ants running the stems to farm them.

The damage

Distorted, puckered new growth and a sticky sheen, often with ant traffic; heavy colonies stunt young plants and can carry plant viruses from bed to bed.

The move

A hard blast of water knocks most colonies off; insecticidal soap handles the rest. Then let the beneficials do the real work — ladybugs, lacewings, and hoverflies clear aphids fast, so skip the broad sprays that kill them too. A little patience early buys you the good bugs.

What it looks like

Flat, shield-shaped gray-brown bugs on squash and pumpkins, with tidy clusters of bronze, football-shaped eggs tucked into the vein angles on the leaf undersides. Crush one and you will know the smell.

The damage

Wilting, yellow-speckled leaves — young plants can collapse — and the neat coppery egg clusters on the undersides, the easiest life stage to catch.

The move

Scout the leaf undersides and scrape off the egg clusters — the single most effective habit. Hand-pick adults (a board laid beside the plant overnight collects them to dispatch at dawn), clear the debris they overwinter in, and row-cover young plants until flowering.

What it looks like

Clouds of tiny white moth-like insects that lift off in a puff when you brush the plant, then settle back on the leaf undersides. Common on tomatoes, greenhouse crops, and many ornamentals.

The damage

That shaken-plant white cloud, yellowing and weakening leaves, sticky honeydew below with sooty mold on it; heavy numbers stunt plants and can spread viruses.

The move

Yellow sticky traps catch the adults and read you the numbers; a hard water spray and insecticidal soap on the undersides knock them back. Protect the beneficials — lacewings, ladybugs, and tiny parasitic wasps do steady work — pull the worst-infested lower leaves, and ventilate greenhouses, where whiteflies thrive.

What it looks like

Not insects but tiny spider relatives, almost too small to see. The first sign is fine pale stippling that gives leaves a dusty, bronzed cast; in bad cases you will find fine webbing on the undersides and at the leaf joints. They boom in hot, dry, dusty conditions.

The damage

Stippled, bronzed, drying leaves and fine silk webbing; a badly hit plant looks scorched and can drop its leaves.

The move

They hate humidity and water, so a regular hard spray to the leaf undersides sets them back hard, and keeping plants unstressed and well-watered denies them the hot, dry conditions they need. Insecticidal soap or horticultural oil helps — avoid broad insecticides, which wipe out the predatory mites that are their main natural check.

What it looks like

You will meet the damage before the animal — they feed at night and hide in cool, damp cover by day. Hostas, lettuce, seedlings, and strawberries take the brunt.

The damage

Ragged, smooth-edged holes in low leaves and fruit, seedlings grazed to the ground, and silvery dried slime trails glinting on leaves and soil in the morning.

The move

Patrol at night or after rain and remove them, set out iron-phosphate baits (safe around pets and wildlife), and cut their daytime shelter — boards, mulch piled against stems, weedy edges. A copper strip repels them from a bed or pot, and letting the surface dry between waterings makes the whole bed less hospitable.

What it looks like

Dome-shaped mounds of loose soil with no obvious opening, in sunny open ground across the South. Disturb one and the ants boil out and sting. They are more a hazard to the gardener and a nuisance in beds than a plant-eater, though they tend honeydew pests and disturb roots.

The damage

Painful stings, mounds that get in the way of beds and tools, and colonies that shelter and protect aphids and other honeydew-producing pests.

The move

Season-long baiting beats mound-by-mound whack-a-mole: broadcast bait while the ants are actively foraging so the colony carries it to the queen, then spot-treat the stubborn mounds. Keep beds and paths tidy so the ground is less inviting.

What it looks like

Microscopic soil roundworms you will never see. Above ground, plants yellow, stunt, and wilt in patches despite good care; below ground, the roots are knotted with swollen galls — not to be confused with the beneficial nodules on beans and peas. Worst in warm, sandy soils.

The damage

Stunted, drought-prone plants in patches, and roots studded with galls that keep the plant from taking up water and nutrients.

The move

Rotate to non-host cover crops, plant resistant varieties (the "N" in a tomato tag’s VFN), solarize infested beds under clear plastic through the hottest weeks, and build soil organic matter, which feeds the fungi and predators that hold nematodes in check. Raised beds with clean soil are a clean start.

What it looks like

Small yellow beetles marked with either black stripes or a scatter of black spots, swarming the flowers and leaves of cucumbers, squash, and melons. The chewing is real, but the bigger threat is what they carry.

The damage

Chewed leaves and flowers and scarred fruit — and, more seriously, the bacterial wilt and mosaic viruses they spread as they feed, which do far more harm than the chewing.

The move

Row-cover young plants until flowering (then lift for pollination), use yellow sticky traps and a trap crop to pull the beetles off the main planting, and treat them as a disease vector, not just a chewer — manage them promptly. Mulch and resistant varieties help; clear the debris where adults overwinter.