Egg-laying by some Dipterous pests of cultivated Cruciferae in north-east Scotland.
Abstract
The following is virtually the author's summary. Dipterous eggs laid in the soil round the bases of plants in market-garden crops of cabbage and cauliflower and field crops of swede, turnip and kale were systematically sampled in north-eastern Scotland during 1962-65. In all the crops studied, a sequence of species was found. Eggs of Hylemya (Erioischia) brassicae (Bch.) were the first to be laid, followed by those of H. (Delia) platura (Mg.) and H. florilega (Zett.) (trichodactyla (Rond.)) and finally a species tentatively identified as Muscina sp. Egg-laying by H. brassicae commenced in mid-May in market-garden crops, with the peak period for first-generation eggs during June and for the second generation between late July and mid-August. The counts indicated that there were two generations of H. platura and H. florilega closely associated with those of H. brassicae. The main period of egg-laying by Muscina sp. was during late July and August, although in 1963 it occurred throughout September in both types of crop. The sequence of species occurred later in the season in swede crops, as these were not available when oviposition by H. brassicae, H. platura and H. florilega began in market-garden crops. Eggs of H. (E.) floralis (Fall.) were laid in swede crops, but not in market-garden crops. Observations on cabbage and cauliflower crops of different ages showed that as the plants matured they became less attractive as oviposition sites for H. brassicae. In 1963, most of the eggs collected were of H. brassicae or H. floralis, which could not be separated, but in 1964, eggs of H. platura or H. florilega were also common.