The effect of cultivation of different cover crops in pear orchards in population regulation of pear psylla, Cacopsylla pyricola

Sowing cover crops is one of the agricultural practices in habitat management for enhancing the diversity of beneficial arthropods. In this study, the impact of sowing cover crops between the lines of pear trees, Pyrus communis L., was assessed on the densities and damage of the pear psylla, Cacopsylla pyricola (Förster), and natural enemies on the pear orchards over two growing seasons (2022 and 2023). Experimental cover crops were (1) red clover, Trifolium pratense L., (2) rosemary, Rosmarinus officinalis L., (3) canola, Brassica napus L., (4) mix cultivation clover-rosemary-canola, and (5) absence of cover crops (as control). The results indicated that the lowest densities of the eggs, nymphs, and adults, and the percent of infested leaves and fruits of the pear psylla per 30-cm branch were observed in the plots with mixed cultivation of clover-rosemary-canola. Moreover, the highest total abundance of predators was recorded in the mix of clover-rosemary-canola plots. Among the collected natural enemies, Anthocoris nemoralis (Fabricius), Orius niger (Wolff), Hippodamia variegata (Goeze), Chrysoperla carnea (Stephens), and Episyrphus balteatus De Geer, respectively indicated the higher abundance. The greatest values of the Shannon diversity index (H΄ = 2.22 in 2022 and 2.20 in 2023) and the Pielou's evenness index (J' = 0.96 in two years) for the combination of predators were calculated in the mix clover-rosemary-canola plots. Therefore, it could be concluded that cultivating of the mix clover-rosemary-canola between pear trees results in the rise of diversity and abundance of predators and the reduction of pear psylla.