Know your orchard's most persistent lodger

There is a particular sort of disappointment in cutting into a fat, home-grown apple and finding a brown tunnel running through the core, with a plug of gritty frass at the blossom end. That is the work of the codling moth caterpillar, and in a warm British summer it can take a serious share of your crop. The good news is that this is a pest you can manage with patience, timing and a bit of observation rather than a sprayer full of chemicals.

Understanding the life cycle is half the battle. Codling moths overwinter as fully grown larvae tucked into bark crevices, props, shed walls and old fruit crates. They pupate in spring and emerge as adults from late May onwards, flying on warm evenings when temperatures hold above about 15°C. Females lay single eggs on leaves near the fruitlets and on the young apples themselves. The tiny caterpillars hatch a week or two later, chew into the fruit, feed for three to five weeks, then leave to pupate on the trunk. In much of southern England a second generation follows in August; in Scotland and the far north you may only see one. That difference in timing is why a calendar alone is not enough.

Pheromone traps: your early warning system

A pheromone trap will not clear your trees on its own, but it will tell you exactly when the moths are flying in your garden, which is worth more than any general advice. The lure is a synthetic copy of the female's scent, and the sticky base catches males looking for her.

• Hang traps in late May, a fortnight before you expect moths, in the upper third of the canopy at about head height.
• Use one trap per three to five trees, or one per large standard tree, placed on the warmer, south-facing side.
• Check weekly and record the numbers. Lures lose their potency after four to six weeks in warm weather, so replace them and keep spares in the fridge.
• A catch of five or more moths a week is your signal to step up the other measures below. There is no useful threshold if you are catching almost nothing — that is simply good news.

In a small, isolated garden you can try hanging several traps per tree to disrupt mating, but treat this as a bonus rather than a cure.

Netting at precisely the right moment

Exclusion works beautifully if you get the timing right and hopelessly if you do not. Net after pollination is finished and after any thinning — usually from mid-June — and keep the tree covered until the end of August, or until you harvest. Fruit that is already carrying a caterpillar will not be saved, so early netting matters.

Mesh size is the detail people get wrong. Ordinary butterfly netting at 7mm or more will not stop a codling moth, which can squeeze through gaps barely wider than its own body. Look for a mesh of 4mm or less. The net must be framed clear of the canopy rather than draped over the fruit, because a moth can lay eggs straight through the mesh onto any apple pressed against it. Close every gap, and tie the skirt firmly around the trunk. For a single small tree, or a few prized apples on a larger one, slipping fine mesh sleeves or paper bags over individual fruitlets in late June is fiddly but remarkably effective.

The fallen fruit rule

This is the cheapest and most powerful habit you can build. A caterpillar inside a dropped apple leaves the fruit within a day or two and heads for the trunk to pupate, so fallen fruit left lying for a week is simply a nursery for the next generation. Walk the trees with a bucket every day or two from the June drop onwards.

• Drown the fruit in a bucket of water for a few days before composting, or bury it at least 30cm deep.
• Feed it to pigs or poultry if you keep them — they deal with both fruit and larvae without complaint.
• Never add infested fruit to an open compost heap, and never leave it in a crate under the tree.

From July, tie corrugated cardboard bands around trunks to give wandering larvae somewhere to spin their cocoons, then strip and burn the bands in winter. A winter tidy-up of loose bark, old props and shed corners will catch many more.

Make room for the predators

Codling moth has plenty of natural enemies in Britain, and the most important thing you can do for them is to put the insecticide away. Broad-spectrum sprays kill the hunters as readily as the pest, and often trigger a worse infestation the following year.

• Hang nest boxes for blue and great tits — a single brood can take hundreds of caterpillars in a season.
• Hang inverted flowerpots stuffed with straw in the branches for earwigs, which hunt eggs and small larvae by night.
• Leave some long grass, leaf litter and log piles to shelter ground beetles, spiders and centipedes that take larvae as they descend to pupate.
• Grow nectar-rich flowers nearby to feed parasitic wasps and hoverflies.

You will lose a few apples to birds pecking, but the trade is almost always in your favour.

Codling moth in a cider orchard

Traditional cider orchards — the tall standards of Herefordshire, Somerset, Devon and Kent — are a different proposition. You cannot net a fifty-year-old tree, and you would not want to. But cider makers should not be complacent: maggoty fruit invites brown rot and mould, which spoils the juice, and an apple riddled with tunnels adds nothing to the press. Hygiene, therefore, does the heavy lifting. Grazing is the old answer, and pigs or poultry under the trees will clear fallen fruit for you while adding fertility, exactly as generations of orchard keepers intended.

A little damage is part of the bargain. A traditional orchard buzzing with insects and birds is a living habitat, and cider has always been made in places where wildlife and fruit trees share the same ground. Keep a notebook of your trap counts and first sightings each year, because the dates shift with the weather, and you will soon be reading your own orchard better than any general rule can.