Hoverflies (Diptera, Syrphidae) in agrocenoses of the forest-steppe of Western Siberia and the influence of agrotechnological practice on their abundance

Abstract

In the forest-steppe of Western Siberia, the dominant species among 29 species of predatory hoverflies recorded in cereal agrocenoses and on the bird cherry (the primary host of Rhopalosiphum padi) are Episyrphus balteatus, Scaeva pyrastri, Sphaerophoria scripta, Melanostoma mellinum, and flies of the genus Platyheirus. The bioecological features and the data on the dynamics of the hoverfly abundance in the winter rye, spring wheat and oats, and perennial and biennial grass agrocenoses are presented. The influence of agrotechnological measures on these characteristics is shown. The numbers of cereal aphids and hoverflies are the highest on spring wheat cultivated using a complex of fertilizers and pesticides. The basic soil treatment and precursors in crop rotation did not affect the abundance of hoverfly larvae. On wheat grown with application of a complex of chemicals the abundance of Syrphidae was greater than when it was grown after fallow as the fourth culture. In crop rotation, hoverflies preferred the crops with mass breeding of aphids and flowering grasses: wheat after fallow, oats, and barley with melilot. At low population density of cereal aphids the number of Syrphidae on all the cultures was low. Despite the constant presence of flies on wild herbs, melilot, sainfoin, alfalfa, clover and the abundance of aphids on these grasses, larvae of hoverflies were scarce. On wild herbs and brome grass, larvae of hoverflies were not found. This fact appears to be associated with the microclimatic conditions of dense grass cultures.