Maternal effects and performance of Delia platura (Diptera: Anthomyiidae) in a native and an introduced crop

Delia platura is an important pest in crops around the world. Its host range includes almost 50 plants. However, it can also develop in soil organic matter. In Ecuador, D. platura is a serious problem for the crop, Lupinus mutabilis, and also attacks broccoli (Brassica oleracea). After broccoli is harvested, crop residue is collected and mixed with soil or stored close to fields. It is unknown whether D. platura is attracted to L. mutabilis or broccoli residue or what are the adaptive responses of larvae on different hosts. Attraction and performance of D. platura reared on broccoli residue and L. mutabilis were evaluated. For the attraction test, fertilized females were placed in an olfactometer. Seedlings of L. mutabilis and broccoli residue were used as stimuli and an empty jar and sterilized soil as controls. For the performance test, eggs were placed on seedlings of L. mutabilis and broccoli residue. Delia platura females preferred broccoli residue to L. mutabilis even if reared on L. mutabilis. The number of larvae, pupae and adults were higher when reared on broccoli. Conversely, pupal weight, time from larva to pupa, pupa to adult and total life cycle were longer in flies reared on L. mutabilis. Volatiles from broccoli residue may attract D. platura females and stimulate oviposition in L. mutabilis. Although D. platura developed better in broccoli, L. mutabilis can also be a good host since pupae were heavier in comparison with flies reared on broccoli residue.