Effectiveness of aphid parasitoids (Hymenoptera: Aphidiidae) on winter wheat in two agricultural systems

From the obtained results we can note that the parasitoids in our experiments in 1 997 and 1998 had considerable influence on decline of aphids population density, at which the percent of parasitization in milk maturity stage of wheat was from 2.7 to 35%. The culmination of parasitization was recorded in our experiments about 7–10 days after the culmination of population density of aphids. The obtained results did not confirm the definite influence of different growing systems on parasitization of aphids, because in 1997 the parasitization was very high in integrated growing system and in 1998 in ecological growing system. The influence of different growing systems on aphids parasitization appeared during a given year and within an growing system. It also appeared between different years and it was found that these differences were significant. The parasitoids found were: Aphidius ervi Haliday, A. rlwpalosiphi De Stefani-Pcrcz, A. uzbekistanicus Luzhctzki, Praon volucre (Hal iday), Ephedrus plagialor (Nees), Diaeretiefla rapae (M'lntosh). In 1997, the most abundant species were Aphidius ervi and A. rhopafosiphi and in 1998 A. ubekistanicus and Aphidius ervi.