The effects of the insecticide Lannate registered 20 L on target and non-target organisms were studied in sprayed and drift areas of kohlrabi (Brassica oleracea). The study comprised eight field plots (each 12.5 m x 6m), providing four replicates of a water control and the application with Lannate registered 20 L at 0.45 kg/ha. Each plot comprised a 4 m wide sprayed area and a 2 m wide "drift" area, left unsprayed. The parasitoid Aphidius colemani (Hymenoptera; Braconidae) and its host aphid Myzus persicae (Hemiptera; Aphididae) served as indicator organisms. The residual toxicity of Lannate registered 20 L to A. colemani and M. persicae was quantified in an exposure experiment. Plants were taken from the field at different time intervals following the insecticide treatment to expose test organisms to plant surfaces in the laboratory. Mortality rates of A. colemani were 94% on plants removed on the day of the application from the treated area and 79 and 69% on plants 0.6 and 2 m downwind from the treated area. No toxic effects on parasitoids were observed 4 days after treatment (a.t.). M. persicae were less susceptible to Lannate registered 20 L residues compared to A. colemani. M. persicae mortality was 46% on plants collected from the sprayed area on the day of the application and 5 and 8% on plants collected from the drift area. In addition, densities of aphids and aphid mummies in the treated and drift areas of field plots were assessed from 1 day pre-treatment to 14 days post-insecticide application. Spraying significantly decreased aphid densities, but the population built up again, Compared to the control, no effect was detected on aphid population densities in the drift area of field plots. Densities of mummies in the insecticide treated area of plots were lower compared to densities in the control from 1 day post-application. There was no effect on mummy densities in the drift area. Recolonisation of field plots following the insecticide treatment was estimated by the release of A. colemani. Since A. colemani is not indigenous in northern Germany it was possible to determine their dispersal into the crop by mummy collections. Recovery of A. colemani mummies was low. Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Ecology; Habitat; Man made habitat; Pollution; Chemical pollution; Abiotic factors; Chemical factors; Land and freshwater zones; Palaearctic region; Europe Aphidius colemani (Aphidiidae); Hemipteran hosts; Myzus persicae; Population dynamics; Cultivated land habitat; Fertilizer and pesticide pollution; Fertilizers and pesticides; Germany; Hannover; Insecticide drift, impact on population dynamics, kohlrabi fields Myzus persicae (Aphidoidea); Hymenopteran parasites; Aphidius colemani, impact on parasite population dynamics; Plant hosts; Brassica oleracea; Cultivated land habitat; Fertilizer and pesticide pollution; Fertilizers and pesticides; Insecticide drift; Germany; Hannover; Hymenopteran parasite population dynamics, impact of insecticide drift, kohlrabi fields none