Excito-repellent and Pesticide-Likeness Properties of Essential Oils on Carpophilus dimidiatus (Fabricius) (Nitidulidae) and Oryzaephilus mercator (L.) (Silvanidae).

Carpophilus dimidiatus (Fabricius) (Nitidulidae) and Oryzaephilus mercator (L.) (Silvanidae) are insect pests that cause severe damage in important walnut growing regions in the northwest of Argentina. The current management approaches for these pests involve the use of unsafe phosphorus pesticides whose overuse have led to farmworker poisoning, pest resistance issues, and environmental contamination. Plant extracts, particularly essential oils, are an alternative source of insect control agents. Excito-repellent essential oils can be used to develop ecofriendly tools for managing the pest population without affecting quality and visual appearance of the stored walnuts. Laboratory studies were conducted to assess the excito-repellent effects of C. dimidiatus and O. mercator of 12 essential oils derived from aromatic plants used as food additives and traditional medicine in Argentina: Aloysia citrodora (AC), Aloysia gratissima (AG), Aloysia gratissima var. Gratissima (AGG), Blepharocalyx salicipholius (BS), Hyptis mutabilis (HM), Lippia junelliana (LJ), Lippia turbinata (LT), Mentha x piperita (MP), Minthostachys mollis (MM), Minthostachys verticillata (MV), Origanum vulgare(OV), and Rosmarinus officinalis (RO). The most bioactive EOs (ERijk ≥ 70%) were Aloysia gratissima var. Gratissima (AGG), Minthostachys verticillata, and Lippia junelliana. Their bioactivity profile and chemical space, characterized from GC-MS measures, Generalized Estimating Equations, and Hierarchical Cluster Analysis, revealed that they are mixtures of very functionalized molecules with physicochemical properties similar to those of insecticides with low residual property that enter the insect body through the respiratory system by inhalation. The AGG, MV, and LJ oils are promising as protective agents of walnut products. In our laboratory, studies of their formulations for use in integrated pest management programs are still ongoing.

Chemical composition and insecticidal activity of essential oils from cultivated and native aromatic plants of Argentina against Carpophilus dimidiatus (Fabricius) (Nitidulidae) and Oryzaephilus mercator (L.) (Silvanidae).

Essential oils from aerial parts of six aromatic plants were analysed by GC-MS. The major compounds identified were γ-terpinene (11.5%), cuminaldehyde (26.6%) and γ-terpinen-7-al (40.6%) in Cuminum cyminum, trans-anethol (95.2%) in Pimpinella anisum, α-pinene (11.6%), limonene (21.0%), ß-caryophyllene (22.3%) and α-humulene (16.7%) in Lippia integrifolia, limonene (40.8%) and artemisia ketone (19.3%) in Lippia junelliana, trans-ß-ocimene (15.6%), 4-ethyl-4-methyl-1-hexene (24.5%), trans-tagetone (20.5%) and verbenone (27.2%) in Tagetes minuta, 1,8-cineole (17.9%),elixene (10.3%) and spathulenol (13.8%) in Aloysia gratissima. Oils with strong insecticidal activity on Carpophilus dimidiatus and Oryzaephilus mercator were from P. anisum (LC50 = 4 µl/L; LC100 = 10 µl/L) and T. minuta (LC50=10.19-12.57 µl/L; LC100=20 µl/L). Scents of C. cyminum and L. junelliana were strong insecticides on O. mercator (LC50=7.02-7.17 µl/L; LC100=10.00-20.00 µl/L). The insecticidal activity was associated to the whole content of C10 molecules and oxygenated constituents. The P. anisum oil is promising as protective agent of nut products.