Signs and symptoms
Infested fruit will often have puncture marks (‘stings’) made by the entry of the female’s ovipositor. Sometimes there may be decay or sugary exudate around the stings. However, it is not always possible to recognise infested fruit, although infestation can usually be determined by cutting open fruit and looking for eggs or larvae (White and Elson- Harris 1994).
Fruit can be stung by more than one species (Christenson and Foote 1960).
Some fruit, such as avocado and passionfruit, develop hard, thickened areas where they are stung. In mature citrus, the sting mark may be a small brown depressed spot, or have an indistinct, bruised appearance, while on green citrus fruit the skin colours prematurely around the sting mark. In humid conditions, the fungi responsible for green mould in citrus and brown rot in stone fruit will readily infect stung fruit. Fruit may eventually fall from the tree as a result of larval infestation.
The extent of the damage caused by larvae tunnelling through fruit varies with the type and maturity of the fruit, the number of larvae in it, and the prevailing weather conditions.
Larvae burrow towards the centre in most fruits, with internal decay usually developing quickly in soft fruits. In hard fruit a network of channelling is usually seen, followed by internal decay. Larval development can be very slow in hard fruits such as Granny Smith apples.