How to identify and deal with Caterpillars

Caterpillars

Lepidoptera larvae

also called Moth larvae, Loopers

Moth and butterfly larvae that chew holes in leaves, buds, and fruit — species varies by host. Pick off by hand where seen and net vulnerable plants.

Insect Leaf-eater Disfiguring SpringSummerAutumn

How to know it

A catch-all for the moth and butterfly larvae that graze foliage: green loopers that walk in arches, brown winter-moth caterpillars in spring apple blossom, tortrix larvae inside a leaf spun shut with silk, box tree moth caterpillars behind webbing. Six true legs at the front, fleshy prolegs behind — that is what separates a caterpillar from a sawfly larva.

What you'll see

Holes chewed through leaves, in from the margin or out of the middle, with droppings below.
Leaves spun together or rolled shut with silk, a caterpillar wriggling backwards when opened.
Buds and blossom hollowed in spring, so the fruit never sets.
Webbing over shoots, with stripped stems and brown foliage inside — box tree moth’s signature.
Sudden defoliation of one plant while everything around it stands untouched.

Where it comes from

Moths lay on or near the host and the larvae feed for a few weeks before pupating in soil, litter or a spun cocoon. Some species have one generation a year and overwinter as eggs on bark; others, box tree moth among them, run two or three generations and can strip a hedge twice in a season.

Sporadic and species-specific. Warm springs bring winter moth larvae out with the blossom; warm summers let box tree moth and tortrix run extra generations.

Dealing with it

Hand-pick — for a shrub or a row of vegetables this is quick, precise and costs nothing.
Open rolled or webbed leaves and squash what is inside; a spray will not reach it.
Use Bacillus thuringiensis on heavy infestations, which spares bees, ladybirds and everything that is not a caterpillar.
Hang pheromone traps for box tree moth so you spray or pick at the right moment rather than blindly.
Grease-band apple trunks in autumn to stop wingless female winter moths climbing up to lay.

Keeping it out

Grow umbels and daisies to keep parasitic wasps and tachinid flies resident — they parasitize caterpillars constantly.
Encourage garden birds with water and cover; a nesting tit family takes thousands of caterpillars.
Net the few crops that are reliably attacked rather than spraying the whole garden.
Inspect box, brassicas and fruit weekly in the growing season, when damage is still trivial.
Leave a little damage: caterpillars are what the birds and the wasps live on.

What it goes for

LeavesShoots & stemsFlowersFruit & pods

Almost anything, but box, apples, brassicas, roses, gooseberries and greenhouse crops see it most.

and 5 more in the catalog

Who hunts it for you

Assassin bugReduviidae A patient ambusher with a curved beak it drives into whatever it catches — caterpillars, beetles, bugs, and the occasional bee, so count it a generalist rather than a specialist. It will jab a careless finger too, so admire it and leave it be. Grow to recruit it: Dill,Fennel,Goldenrod,Sweet alyssum,Tansy,Yarrow
BatsChiroptera A single bat takes hundreds of moths and mosquitoes in a night, and the moths are the parents of your cutworms, corn earworms and hornworms. Put up a bat box on a warm south wall, leave a night-scented corner unlit, and never spray after dark. Grow to recruit it: Evening Primrose,Honeysuckle,Nicotiana,Summer Jasmine
Big-eyed bugGeocoris spp. A stubby 3 mm bug with enormous wrap-around eyes, working the soil surface and the low foliage for aphids, mites, thrips and insect eggs. It is the main natural check on chinch bugs in a lawn and it is killed outright by insecticide. Grow to recruit it: Calendula,Clover,Cosmos,Goldenrod,Sweet alyssum
Damsel bugNabidae A slender, mantis-armed bug that grabs aphids, small caterpillars, and thrips in low crops and meadowy edges. Leave a strip of unmown grasses and flowers for it to overwinter in. Grow to recruit it: Fennel,Sweet alyssum,Yarrow
Garden birdsPasseriformes Both things are true: birds strip your currants and a brood of blue tits takes several thousand caterpillars out of one fruit tree in a fortnight. Net what you must and welcome them everywhere else — a nest box near the apples is worth more than a spray. Grow to recruit it: Echinacea,Elderberry,English holly,Goldenrod,Rudbeckia,Sunflower
Green lacewingChrysoperla carnea Its bristly larvae — "aphid lions" — impale aphids, mealybugs, thrips, and mite colonies, eating hundreds a week. Adults feed on nectar and pollen from small open flowers and overwinter in hollow stems left standing. Grow to recruit it: Cilantro,Cosmos,Dill,Sunflower,Yarrow
HedgehogErinaceus europaeus A European animal, and worth saying so plainly: there are no hedgehogs in North America, and the ally that does the same night shift here is the toad, the opossum or the ground beetle. Where they do occur, cut a gap in the fence and skip the pellets.
Minute pirate bugOrius spp. A pinhead-sized true bug that is the best natural check on thrips, and happily spears aphids, mites, and insect eggs too. It needs pollen when prey is scarce, so keep something flowering nearby. Grow to recruit it: Cosmos,Fennel,French marigold,Sweet alyssum
Parasitic waspsBraconidae & Trichogramma Tiny, stingless wasps that lay eggs in or on caterpillars, aphids, and moth eggs — the white cocoons riding a hornworm are their calling card, so leave that caterpillar be. Umbel flowers with shallow nectar keep the adults fuelled. Grow to recruit it: Cilantro,Dill,Fennel,Lovage,Parsley,Sweet alyssum
Praying mantisMantidae A sit-and-wait ambusher that snatches caterpillars, beetles, and anything else that wanders close — friend and foe alike, so count it a mixed blessing. Tall, structured plantings give it perches and egg-case anchors. Grow to recruit it: Cosmos,Fennel,Sunflower
Snakes & lizardsColubridae & Phrynosomatidae A garter snake works the beds for slugs and voles and a fence lizard clears grasshoppers off a sunny wall. Almost every snake a gardener meets is harmless and useful; give them a log pile, a warm flat stone and a bit of cover and they stay.
Soldier beetleCantharidae Soft-winged beetles seen mating on flower heads in high summer; adults and larvae both take aphids and soft grubs. Open composite flowers are their landing pads and hunting grounds. Grow to recruit it: Echinacea,Rudbeckia,Sunflower,Yarrow,Zinnia
SpidersAraneae Webs, ambushes, and night patrols make spiders the garden’s steadiest generalist predators, taking whatever flies or crawls past. Mulch, ground cover, and undisturbed corners keep the population dense. Grow to recruit it: Lavender,Thyme
Spined soldier bugPodisus maculiventris A predatory stink bug — same shield outline as the pest, but with a sharp spine at each shoulder and a beak it uses to spear caterpillars and beetle grubs. Learn the spines before you squash a shield bug, because this one is on your side. Grow to recruit it: Dill,Fennel,Sweet alyssum,Yarrow
Tachinid flyTachinidae Bristly, house-fly-lookalike parasitoids that lay eggs on caterpillars, beetle grubs, and earwigs — the maggot consumes the host from within. Adults sip nectar from shallow umbels and daisies. Grow to recruit it: Cilantro,Dill,Feverfew,Parsley,Sweet alyssum