Ecological Considerations in the Management of Delia Pest Species in Vegetable Crops

Flies belonging to the genus Delia are members of the Anthyomyiidae, a taxonomically difficult subfamily of the Muscidae (Diptera) as many of the characters used to differentiate the genera and species are not always constant ( l3). The various keys (76, 81) for separating the species can be difficult to use, even when large numbers of different species are available. To the field ecologist, keys to indicate how pest species differ from other insects collected in samples (5) may be more useful than keys restricted solely to anthomyiid species. Certain common Delia species are pests of economic importance. The larvae of D. coarctata and D. platura attack cereals, those of D. radicum and D. floralis the roots of bras sica crops, and those of D. antiqua, D. platura, and D. florilega the roots of onions (13). This review concentrates on Delia species that attack vegetable crops and in particular on D. radicum (the cabbage maggot) and D. antiqua (the onion maggot), the two pests that have been studied in greatest detail. As parallel work has often been carried out on both species, certain points will be illustrated by reference to only one species to save space. Like most pest species, these anthomyiid flies have experienced frequent changes of name. Within the last 20 years, the genus of the cabbage maggot has been called Hylemya in the United States and Canada; Hylemyia in Norway; Phorbia or Chortophila in France, Germany, and Russia; and Delia or Erioischia in Belgium and England (0). Until 1981, brassicae was