CEREAL APHIDS, THEIR PARASITOIDS AND COCCINELLIDS ON OATS IN CENTRAL POLAND

The aim of this work was to study the complex role of coccinellids and parasitic Hymenoptera in reducing the populations of cereal aphids on oat crops. The studies were conducted in 1988-1991 in Dziekanow Polsk i near Warsaw. The dynamics of number of aphids and coccinellids and d egree of parasitization of aphids by parasitoids were examined. Moreov er, the species composition of the studied groups of insects was also determined. The studies allowed to determine the occurrence of three s pecies of cereal aphids: Rhopalosiphum padi L. Sitobion avenae F. and Metopolophium dirhodum Walk. The first two were the most numerous. The dynamics of the individual species was different in the separate year s of the study. The first to appear was usually R. padi. On the studie d fields eight species of predatory Coccinellidae and seven species of parasitic Hymenoptera belonging to the family Aphidiidae were found. The studies revealed considerable differences in the abundance of the species of cereal aphids in the individual years, course of its dynami cs and also synchronization between the development of aphids and thei r natural enemies. The role of aphidophages should be separately consi dered for the individual aphid species. R. padi is usually attacked by coccinellids after the peak of numbers, whereas S. avenae during the increase of population. S. avenae is also reduced to a considerable ex tent by parasitoids.