About this product
The small brown tunnel through the core of a home-grown apple is codling moth, Cydia pomonella, and it is the most destructive pest of British apple, pear and quince trees. The adult lays on developing fruitlets in early summer and the pinkish-white caterpillars bore straight into the young fruit.
The treatment does not target them in the fruit. It targets the moment they leave it. In late summer and autumn the mature larvae crawl out and travel down the trunk to find a sheltered crevice in the bark, the leaf litter or the soil, where they pupate and overwinter. That journey is the one point in the year when they are exposed, and that is when nematodes catch them. This mixed-species pack also handles oriental fruit moth, Grapholita molesta, which overwinters the same way.
September to October is the only window there is. Miss it and you wait a year. Air temperature must be between 14°C and 30°C, so a mild autumn is ideal and a cold snap below 14°C sends the nematodes dormant.
Pick a mild, overcast day. Wet the trunk and the ground beneath it first, mix as instructed, then apply with a watering can with the rose off, a hand sprayer or a backpack sprayer, coating the bark, the lower limbs and the soil at the base thoroughly. The larvae are travelling down that bark, so coating it well matters more than covering ground. Apply in the evening. Keep the trunk and the ground moist for one to two weeks afterwards. A second application a fortnight later catches the late-crawling larvae and makes a real difference, which is why the 2-pack and 3-pack exist. Each pack treats up to 60 square metres, enough for one substantial tree or several trained ones.
Nematodes are one part of it. Clear fallen fruit promptly, because any maggot inside becomes next year's moth. Wrap corrugated cardboard bands round the trunk in midsummer, then remove and burn them in autumn with the larvae inside. Use pheromone traps to monitor adult flight so you know when larvae are coming. Feed the birds near your fruit trees in winter and the tits will work the bark for you in spring.
Do not expect to see anything happen. The proof arrives next year, in how few apples come down with tunnels through them.