Codling moth

What codling moth is

Codling moth (Cydia pomonella) is a small, greyish-brown moth a little under 1cm long, easy to overlook when it rests on bark. The adult itself does no harm — it's the caterpillar, a pinkish-white grub with a brown head, that ruins the crop. It bores straight into the developing fruit and feeds on the seeds in the core, leaving a tunnel packed with brown droppings and a small entry hole that often weeps a little sticky frass. Apples are the main target, but pears and occasionally walnuts and quinces are affected too.

The lifecycle

Understanding the moth's calendar is the key to controlling it, because the window for action is short. The moths emerge from late May into June, timed to coincide with the apple trees finishing flowering. On warm, still evenings the females lay tiny flat eggs singly on developing fruit and nearby leaves.

The eggs hatch after a week or two and the young caterpillars burrow into the fruitlets, where they feed safely out of reach for around a month. Once fully grown they crawl back out, drop down and hide away to spin a cocoon — under loose bark, in cracks in the trunk, or among debris at the base of the tree. There they overwinter, pupating the following spring to start the cycle again. In a long, warm UK summer there can be a partial second generation, which is why later-stored fruit is sometimes hit hardest.

Organic control

You won't eliminate codling moth entirely, but you can knock the numbers right down without sprays.

• Pheromone traps. Hang a codling moth pheromone trap in the tree from early to mid-May. The sticky trap, baited with a lure that mimics the female's scent, catches the males. On a single garden tree this genuinely reduces mating and fruit damage; it also tells you exactly when the moths are flying.
• Encourage birds. Blue tits and other small birds hunt out overwintering caterpillars tucked into the bark. A few nest boxes and winter feeders nearby keep them visiting and working the trunk for you.
• Garden hygiene. Clear up and bin or burn windfalls and damaged fruit promptly, before the grubs crawl out to pupate. Scraping away loose, flaky bark and fitting a band of corrugated cardboard or sacking around the trunk in midsummer gives caterpillars a tempting place to cocoon — you then remove and destroy it.

Keeping a tree small and open makes all of this far easier, which is one more reason to choose a tree on a dwarfing rootstock. For more on diagnosis and timing, see our full guide to codling moth and the wider fruit growing guides.