The adult moth lays eggs on developing fruit in June-July.
After hatching, the 12mm (½”) long pinkish-white caterpillar tunnels into the fruit and feeds around the stone.
Probably the first signs you will see of the problem, is orange-brown particles on the fruit, this is the caterpillar's excrement.
Other signs are damaged mis-shapen fruits that may have ripened prematurely.
Late ripening fruits are generally less affected.
In July / August, the fully fed caterpillar emerges and crawls under peeling bark or cracks in the trunk to over winter,and pupate the following spring.
There are no garden insecticides for this pest, pheromone traps are the best solution.
These traps, which are available from most garden centres, should be hung in the tree in mid-May when the adult moths are emerging.
The purpose of the traps is to trap male moths are thus preventing them mating with the females resulting in fewer viable eggs being laid.