Holes in Plant Leaves: What's Eating Your Plant?

Finding holes in a plant's leaves is like coming home to a burgled house: the intruder is long gone, but it left fingerprints. Almost every leaf-eater chews in its own recognisable pattern. Read the hole, and you know the pest — usually without ever seeing it.

Read the hole first

Before reaching for any treatment, look at three things: the shape of the damage (irregular, round, edge-notch, or tunnel), where it is on the plant (low leaves, new tips, edges), and what's left behind (slime, droppings, webbing). Then check under the leaves and at night with a torch — that's when most culprits actually feed.

Irregular holes and slime trails: slugs and snails

Large, irregular holes — often starting between veins — on hostas, seedlings, lettuce and other soft growth, plus tell-tale silvery mucus trails on leaves or soil, mean slugs or snails. They feed after dark and on wet days, and can shred a tray of seedlings in one night. Evening torch patrols, beer traps, copper barriers, and wildlife-friendly ferric phosphate pellets all work; the most effective single move is a night-time hand-collection after rain.

Ragged holes and black crumbs: caterpillars

Ragged, expanding holes — sometimes whole leaves reduced to a skeleton of veins — with small dark droppings (frass) beneath mean caterpillars. On brassicas, look for the cabbage white's yellow-and-black or velvet-green larvae; many others feed at night and hide by day. Hand-pick what you find, check leaf undersides for egg clusters and squash them, and net brassicas before the butterflies arrive. For heavy infestations on vegetables, the biological spray Bacillus thuringiensis targets caterpillars and spares everything else.

Tiny round pits: flea beetles

Dozens of small, round holes and pits a millimetre or two wide — a "shotgun blast" pattern — on rocket, radish, brassica seedlings and nasturtiums mean flea beetles: tiny shiny beetles that spring away when disturbed. Seedlings usually grow through the damage once past four to six true leaves. Keep plants growing fast with steady water, cover young sowings with insect mesh, and delay sowing rocket until late summer when beetle pressure drops.

Perfect semicircles from the edge: leafcutter bees

Neat, almost machine-cut semicircles or ovals scalloped from leaf edges — classically on roses — are the work of leafcutter bees. They use the pieces to line their nest cells and cause no meaningful harm to the plant.

Tip: don't treat leafcutter bees at all. They are excellent pollinators, the cosmetic damage stops within a few weeks, and their presence is a sign of a healthy garden.

Notched edges: adult vine weevils

Regular U-shaped notches bitten into leaf edges of evergreens — rhododendrons, camellias, viburnums, bergenias — mean adult vine weevils feeding at night. The notches are cosmetic; the real threat is their soil-dwelling larvae, which eat roots, especially in pots. If you see notching, treat the compost of nearby containers in late summer with nematodes (Steinernema kraussei) to break the cycle.

Tunnels inside the leaf: leaf miners

Pale, winding tunnels or blotches sandwiched inside the leaf — not holes right through — are leaf miner larvae feeding between the leaf surfaces. Sprays barely reach them; simply pick off and bin mined leaves. On chard and beetroot, crush the white grubs inside the mine with your fingers.

Holes with no pest at all

Not every hole is bite damage. Shothole disease punches clean round holes with brown rims in cherry laurel and Prunus leaves after the fungal spots drop out. Hail, wind-whip, and expanding physical damage on young leaves also mimic feeding. And on Monstera and its relatives, splits and holes are fenestrations — the plant is supposed to look like that.

Warning: skip the "spray everything" reflex. Broad-spectrum insecticides kill the ladybirds, lacewings, parasitic wasps and bees that were quietly controlling your pests, and most hole-makers above are either harmless, self-limiting, or better handled physically.

Still can't match the pattern? Photograph the damaged leaf in PlantMe — the app cross-references the damage against 500+ diseases and pest problems and tells you the culprit and treatment in seconds.