Population of common green lacewing, Chrysoperla carnea and its prey pests under two different patterns of chemical control (Case study: Apple orchards and tomato fields of Quchan)

In a three-year study, the population density and spatial dispersion of the common green lacewing, Chrysoperla carnea and its prey pests (Aphids, Thrips tabaci and Helicoverpa armigera) was investigated in apple orchards and tomato fields under two different conservational and conventional chemical managements, in Quchan, northeastern Iran. The chemical management pattern had a significant effect on the population density of the green lacewing, so that the highest density was observed in conservational pattern in both apple orchards and tomato fields (0.178 and 0.546 individuals/leaf or plant, respectively). The pattern of chemical management in apple orchards also changed the spatial dispersion of the green lacewing, so that its eggs and larvae population had random dispersion in conservational (with Taylor’s coefficients of 1.12 and 1.17, respectively) and aggregated dispersion in conventional (with Taylor’s coefficients of 1.42 and 1.29, respectively) orchards. While, the spatial dispersion of this predator was aggregated in both conventional and conservational patterns in tomato fields. In apple orchards, the increase in the green lacewing population after the implementation of conservational spraying could not prevent the increase in aphids’ population, so that their population increased significantly compared to the conventional pattern. In contrast, population density of the T. tabaci and H. armigera in tomato fields did not have much difference in conservational and conventional chemical patterns. Therefore, in tomato fields, it is recommended to replace the conservational spraying pattern with conventional spraying, but the conservational pattern should be used along with other complementary methods in apple orchards.