RELATIONSHIPS BETWEEN PRIMARY AND SECONDARY PARASITOIDS OF CEREAL APHIDS

The aim of the study was to compare relationships between primary and secondary parasitoids associated with cereal aphids on winter as well as on spring crops. The study was carried out between 1991-1994 in two regions in Poland, 400 km apart (vicinities of Warsaw and Wroclaw). I t has been found that in both regions, there occurred three cereal aph id species Sitobion avenae F., Rhopalosiphum padi L. and Metopolophium dirhodum Walk. The groups of parasitization, were similar in both reg ions. Although more species of parasitoids were found in the Wroclaw r egion (nine species of primary and 11 species of secondary parasitoids ) as compared to the Warsaw region (six and nine, respectively), the s pecies composition was similar in both regions. There were big differe nces in proportion between primary and secondary parasitoids on spring and winter cereals at both localities. In the case of winter cereals, there constituted 30% on average while the hyperparasitoids constitut ed 70%. Aphidius uzbekistanicus Luzh. predominates over other primary parasitoids and Dendrocerus carpenteri Curtis is a dominant species am ong hyperparasitoids. In the average, with the secondary parasitoids 2 8%). Most often, A. uzbekistanicus is a dominating species but in cert ain years the dominance is not as clear as in winter cereals. The domi nance hierarchy within hyperparasitoids is different in different year s. The presented results demonstrate that in spite of a great distance between the study areas, the relationships between the cereal aphids' primary and secondary parasitoids show similar trends.