The Codling Moth is a common pest of Apples. The adults are active on warm nights in June and July. Eggs are laid singly on the leaves and developing fruit, the caterpillars hatching about two weeks later.
The caterpillars tunnel into the fruit straight away and eat their way down to the core. After a month when they have finished eating, the caterpillars leave the fruit and spin a cocoon under loose bark. The majority remain in cocoons until the following season but some will pupate in August to produce a second adult generation.
If insecticides are to be used it may only be possible on smaller trees. Sprays should be applied after flowering, about mid June with a second application three weeks later. Spraying must take place before the caterpillars enter the fruit. Pheromone Traps can reduce the number of male moths and indicate when the adults are active which will help with the timings of sprays. A suitable insecticide would be Sprayday Greenfly Killer produced by Bayer