Population Differences in Emergence of Brassica Root Flies (Diptera: Anthomyiidae)

Abstract

Abstract Accurate timing of pest control measures requires a good understanding of the emergence pattern of the specific pest populations. In 1999–2000, pupae of the cabbage maggot, Delia radicum L., and the turnip maggot, D. floralis Fallen, were collected in the autumn from nine widespread locations in Norway (58–70° N). After diapause development during winter, emergence was studied in a climate chamber at 18°C. The time to 50% emergence was <2 wk for all populations of D. radicum, and the emergence period (time elapsed between 10 and 90% emergence) was ~4 d on average. The results indicated uniform and early emerging populations of this species. D. floralis, however, had much later emergence, with a wide range of emerging biotypes. The time to 50% emergence of D. floralis varied from 5 to 10 wk between populations. Moreover, the emergence period varied between 2 and 7 wk for the different populations, indicating mixtures of differently emerging biotypes. The ecological basis for the diverging emergenc...