Toxicity, Biochemical, and Genotoxic Effects of Eucalyptus smithii Essential Oil and Several Major Monoterpenes on the Land Snail Massylaea vermiculata

Massylaea vermiculata is a significant pest in agriculture, prompting the search for safer, non-chemical methods of control. The present study assessed the lethal and sublethal effects of Eucalyptus essential oil (EEO) and the major components α-pinene and 1,8-cineole on adult M. vermiculata. The most potent compound, α-pinene (LD50: 279.58 µg/g), followed by Eucalyptus EO (LD50: 468.7 µg/g) and 1,8-cineole (LD50: 834.60 µg/g), was assessed topically for acute toxicity. Physiological damage after exposure for 72 hours to sublethal doses (0.2 LD50) was assessed via an integrated multi-biomarker approach. Neurotoxicity was further confirmed by the inhibition of acetylcholinesterase (AChE), with 1,8-cineole resulting in the greatest inhibition. Malondialdehyde (MDA) and glutathione S-transferase (GST) were found to increase, mainly due to the oxidative stress induced by α-pinene. Genotoxicity was reflected in decreased DNA content and an increase in micronuclei and binuclei in hemocytes (particularly with α-pinene). Moreover, genomic template stability (GTS) analysis using RAPD-PCR revealed that α-pinene induced the most severe DNA damage, followed by Eucalyptus essential oil, whereas 1,8-cineole exhibited the least genotoxic effect. These findings demonstrate that EEO and its components exert their molluscicidal effect through multiple modes of action, including neurotoxicity, oxidative stress, and genotoxicity. The best formulation and strategy for field application of compounds from Eucalyptus constitute potential candidates for ecofriendly molluscicides that need to be further explored.