The egg-laying slit in the side of the flower soon turns brown and this is readily visible as an early sign of infestation.
Young larvae tunnel just beneath the surface of the skin of developing fruitlets leaving characteristic ribbon scars.
Larvae bite large cavities inside fruitlets, consuming the flesh and the seeds and producing masses of wet, brown-black frass which is exuded through a large hole in the side of the fruitlet.
Fruitlets with ribbon scars may remain on the tree until harvest but those with more severe damage fall from the tree.
Losses can be severe, particularly when the amount of blossom or crop set is light.