Further investigations of the host range of the carrot fly, Psila rosae (F.)

Techniques were developed for testing umbelliferous species against naturally-occurring populations of carrot fly in the field. The most efficient technique involved exposure of plants to either first or second generations of the insect in the field, followed by caging of infested plots and trapping of emerged flies in water in yellow water dishes. In a series of field experiments between 1981 and 1989 inclusive, a total of 132 umbelliferous species and sub-species were tested against carrot fly. Seventy-eight of these proved to be new hosts, 27 were confirmed as hosts and 27 failed to support any carrot flies. Six non-umbelliferous plant species failed to be colonised by carrot fly. Sources of variability in investigations of the host range of insects are discussed.