crop worldwide. Most cultivars have been derived from sexual
hybridisation and to a lesser extent from chance seedlings
or spontaneous mutation (Janick et al. 1996). The major insect
pests of apples, worldwide, are the codling moth (Cydia
pomonella) and aphids. In Australia, the native light-brown
apple moth (Epiphyas postvittiana) is also a significant pest
(Wearing et al. 1991). Currently, such pests are controlled
by the application of insecticides (Suckling and Brockerhoff
1999). Insects developing resistance to chemical pesticides
provide the increasing impetus for alternative approaches to
pest control (Wearing 1998).