You rarely catch the pest in the act. What you get is the aftermath — holes, squiggles, sticky film, or a seedling that existed yesterday. So the fastest identification works backwards: match the damage pattern first, then confirm the culprit, then decide whether it even needs action. Plenty of garden damage in Australia sits below the level worth treating, and several of the insects you’ll find are on your side.

Start with the damage

Ragged holes in leaves, worst overnight. Caterpillars (look for dark droppings on leaves below) or snails and slugs (silvery trails, damage low on the plant, spikes after rain). Both are the classic seedling killers.

Silvery squiggly lines inside citrus leaves. Citrus leaf miner — the larva of a tiny moth tunnelling between the leaf surfaces. Unmistakable once seen, and mostly a cosmetic issue on established trees. Timing, not spraying, is how you protect new growth: the leaf miner guide covers it.

Sticky leaves, sooty black film, ants running trade routes. Sap-suckers: aphids (clustered on soft new tips), scale (small fixed bumps on stems and leaf undersides) or mealybugs (white cottony tufts in leaf joints). The stickiness is honeydew; the black is a mould growing on it; the ants are farming the insects for it. Manage the sap-sucker and the rest resolves.

Fruit that looks fine, then rots from the inside with maggots. Fruit fly — in most of eastern Australia, Queensland fruit fly. The eggs go in through a sting you can barely see; by the time fruit drops it’s too late for that fruit. This is the pest that most changes how (and when) subtropical gardeners grow soft fruit — it’s a large part of why tomato timing matters so much in Queensland.

Lawn dying in patches; birds, or bandicoots, suddenly very interested in your grass. Usually curl grubs — beetle larvae eating roots. A few are normal in any soil; damage only follows real numbers.

New growth distorted, buds eaten, but no insect by day. Check at night with a torch before blaming anything: earwigs, caterpillars and weevils all work the night shift. In many suburbs the answer is a possum — a protected animal with its own legal rules, and its own guide coming soon.

Fine speckling or bronzing on leaves, maybe faint webbing. Mites — worst in hot, dry, dusty conditions, often after broad-spectrum spraying killed their predators.

The ones you should NOT kill

Ladybirds and their fierce-looking larvae, lacewings, hoverflies, parasitoid wasps, spiders and praying mantises are your unpaid pest control. Two practical consequences. First, identify before you squash — a ladybird larva looks more villainous than most villains. Second, every broad-spectrum spray kills these allies at least as effectively as it kills pests, which is how one spray in spring buys you a mite problem in summer. The bar for spraying anything should be high, and the order of response should start with water jets, hand-picking, exclusion and tolerance.

When to accept damage

A healthy garden carries some insect damage all the time; the goal is harvests and plants that thrive, not unblemished leaves. Reasonable defaults: cosmetic leaf damage on established plants — ignore; damage to seedlings — act fast, they have no reserves; anything trending worse week on week — investigate properly. And if what you’re seeing is yellowing rather than chewing or stickiness, the cause is usually water, nutrition or light rather than any pest — run the yellow leaves diagnostic before treating for insects that aren’t there.

What this hub deliberately leaves out

Specific chemical controls. Where a pest justifies product-level talk (lawn grubs, fruit fly baiting, scale oils), the dedicated article handles it — naming categories of product, never application rates, because rates belong to the registered label on the container, not to a website. If an article anywhere tells you a spray dose in millilitres per litre, close it and read the label instead.