Insecticidal activity of five major essential oil components and their binary mixtures against Jankowska dirhodum and its two biological control agents

Abstract Essential oil components such as terpenes, terpenoids and phenylpropanoids are promising active substances for development of new botanical insecticides. The objective of this study was to identify the insecticidal effectiveness of five major essential oil components and their binary mixtures against Metopolophium dirhodum (Walker) (Hemiptera: Aphididae), an important cereal pest. For the tested compounds, probit analysis was employed to estimate LC 50(90) at 2.32 (8.99) mL L −1 for citral, 1.07 (4.65) mL L −1 for eugenol, 0.91 (2.47) mL L −1 for geraniol, 2.65 (11.74) mL L −1 for geranyl acetate and 2.20 (7.51) mL L −1 for terpineol. Phytotoxicity for experimental plants of Triticum aestivum L. was proven for citral, eugenol and geranyl acetate at concentrations equalling the estimated LC 90 for M. dirhodum . Geranyl acetate was shown to be an important synergist with all the other tested compounds. The best insecticidal effect was observed in the binary mixture of geranyl acetate/terpineol (1:1 ratio), for which the LC 50(90) was estimated at 0.97 (3.72) mL L −1 ; at the same time, no phytotoxicity to the experimental plants of T. aestivum was observed. This binary mixture also turned out to be very friendly to the larvae of Aphidoletes aphidimyza Rondani (Diptera: Cecidomyiidae) and Chrysoperla carnea Stephens (Neuroptera: Chrysopidae), two important aphid predators. Our results show that the geranyl acetate/terpineol mixture is a promising candidate for the development of environmentally friendly botanical insecticides against aphids.