Aphidiids (Hymenoptera, Aphidiidae) in Agrobiocenoses of Field Crops in Leningrad Province

In a long-term research, the species composition, abundance, habitat distribution, and seasonal dynamics of aphidiid parasitoid wasps (Hymenoptera: Aphidiidae) were investigated in field crop agrobiocenoses of Leningrad Province. The family was represented by at least 13 species, while their density was 0.10–0.48 ind. per 10 net-sweeps depending on the biological features of the crop and 0.15–0.28 ind. per 10 net-sweeps in different years. The core of the parasitoid wasp complex associated with aphids comprised four species: Ephedrus plagiator Nees, Aphidius ervi Haliday, A. uzbekistanicus Luzhetzki, and A. rhopalosiphi De Stefani-Perez, which together accounted for 84.8% of Aphidiidae individuals in the herbage of cultivated plants. The abundance of Aphidiidae was the highest in crops of spring wheat and perennial grasses and the lowest in crops of spring rapeseed and narrowleaf lupin. The long-term and seasonal dynamics of the Aphidiidae abundance in grain crop agrobiocenoses turned out to be quite closely related to the dynamics of the abundance of cereal aphids. Of great importance for the seasonal reproduction of Aphidiidae are fields of perennial grasses and winter cereals, where these wasps and their hosts concentrate in spring. Low abundance of Aphidiidae resulted in low levels of infestation of cereal aphids, not exceeding 5% in winter rye crops, 10% in winter wheat crops, and 15% in spring wheat and barley crops.