Phenology and sex ratio of the parasitoids of a cereal leaf miner Chromatomyia fuscula (Diptera: Agromyzidae)

The objective was to compare the phenology of C. fuscula in southern Norway with that of its most important natural enemies: 15 parasitoids of the families Eulophidae and Pteromalidae (Hymenoptera: Chalcidoidea). The use of two Malaise traps in an organically-grown spring barley field and its boundary [balk], through 6 seasons also allowed us to compare these two habitats and to obserwe the effect of harvesting on the parasitoid activity without interference from pesticides. C. fuscula overwinters as an adult and oviposits in May/June. In contrast, the F1 generation of the parasitoids was caught in considerable amounts both in the crop and boundary. The abundance of parasitoids vas highest in July/August; in the crop it usually started decreasing well before harvesting` in the boundary it peaked two weeks or more after harvesting. The results suggest that many parasitoids (especially females) move from the crop to the boundary (or beyond) before harvesting. In both habitats parasitoid species richness usually incereased until harvesting, and thereafter decreased. The pooled parasitoid female proportion was 0.3; in crop and boundarv it was 0.30 and 0.66, respectively, and the majoritv of species had a higher proportion of females in the boundary than in the crop. The phenology of two most common parasitoids is presented.