Insecticidal and antifungal effects of lemon, orange, and grapefruit peel essential oils from Argentina

The aim of the present work was to study the bioactivity of lemon, orange, and grapefruit peel essential oils (EOs) obtained from Argentinian plantations on different agronomically important insect and fungal species. The chemical profile of EOs was determined by Gas Chromatography-Mass Spectrometry (GC/MS); the insecticidal activity was studied through contact and fumigant assays; the antifungal activity was evaluated with fumigant tests. Orange EO was the most effective against Rhyzopertha dominica, Oryzaephilus spp. and Sitophilus granarius in fumigation tests (LC50= 89.39, 94.50, and 163.64 µL/L air, respectively); while the insecticidal effect of EOs was species-dependent in contact toxicity assays. Regarding antifungal activity, Rhizoctonia solanii was more susceptible than Sclerotium rolfsii to the tested EOs, with lemon from Industry 1 and orange being the most toxic EOs (MIC=10.77 µL/plate and 11.02 µL/plate, respectively). Conversely, S. rolfsii was strongly inhibited by lemon EO from Industry 2 (MIC= 52.40 µL/plate). Besides limonene, other compounds that could be responsible for these bioactivities were: linalool, carvone, α-pinene, β-pinene, β-myrcene, α-terpineol, terpinen-4-ol, limonene oxide, β-phellandrene, γ-terpinene, sabinene, neral, neryl acetate, β-caryophyllene and p-cymene. Citrus peel EOs can be used against different pests, contributing to the valorization of citrus residues.