The insecticidal and acaricidal effects of the essential oils (EO) from two populations of Geranium macrorrhizum L (ornamental variety Bevan, VB and wild population from Hungary, GH) have been studied against several insect pests of economic importance in agriculture (Spodoptera littoralis, Myzus persicae and Rhopalosiphum padi), and the hard tick Hyalomma lusitanicum. The oil from the wild population (GH) was characterized by its content in β-elemenone (30.53%), thymol (18.52%) and germacrone (15.54%), while the oil from the commercial variety (VB) had linalool (26.45%) and linalyl acetate (25.11%) as major components. S.litoralis and R. padi were significantly affected by the wild population oil (GH-EO). The oil from the commercial variety VB was less effective against insects. The ixodicidal effects of these oils were strong, being the wild population (GH-EO) the most effective. To correlate the composition of these oils with their activity, the essential oil major components have been isolated (germacrone and β-elemenone) and tested (linalool, thymol, germacrone and β-elemenone). The insect antifeedant and ixodicidal effects of thymol and germacrone explained the bioactivity of the GH essential oil. Therefore, the wild variety of G. macrorrhizum has been selected for domestication given its potential as a source of bioactive extracts and metabolites.

This work has been supported by grants CTQ2015-64049-C3-1-R and CTQ2015-64049-C3-3-R (MINECO/FEDER), Junta de Andalucía (Excellence Project P08-FQM-3596) and Villamagna SA. We thank R. Muñoz for technical assistance and J.M. Tercero for tick collection. The authors are also especially grateful to his Grace the Duke of Westminster.

Peer reviewed