Repellent and Insecticidal Activity of Wild Cannabis sativa L. Essential Oil Against Rhopalosiphum padi and Sitobion avenae, with Exploratory Automated Behavioural Tracking

Wild C. sativa (hemp) represents a promising source of bioactive compounds with potential applications in sustainable pest management, while Rhopalosiphum padi and Sitobion avenae are among the most economically important aphid pests of cereal crops. However, the insecticidal, repellent, and sublethal behavioural effects of essential oil (EO) derived from wild hemp against these aphid species remain insufficiently characterised. Therefore, this preliminary study aimed to evaluate the insecticidal and repellent activities of wild hemp EO and to characterise aphid behavioural responses following exposure. The chemical composition of the EO was determined by GC–MS–FID, while locomotor activity and spatial behaviour were assessed using automated video tracking with EthoVision XT. β-Caryophyllene (37.07%), α-pinene (13.98%), and α-humulene (α-caryophyllene) (8.33%) were identified as the predominant constituents. The EO exhibited pronounced insecticidal activity, causing complete mortality (100%) of both R. padi and S. avenae at all tested concentrations (1.0–5.0%). In contrast, its repellent activity did not exhibit a consistent concentration-dependent pattern. Automated behavioural tracking revealed no significant effects of EO exposure on aphid spatial distribution, locomotor activity, or mobility. Although EO-treated aphids showed a numerical tendency to remain closer to the treated area (mean distance to drop centre: 3.68 ± 0.98 cm versus 4.41 ± 1.11 cm in controls), this difference was not statistically significant. Similarly, total distance travelled and mean velocity remained comparable between EO-treated and control groups, indicating the absence of detectable sublethal on locomotor activity. Overall, the results demonstrate that wild hemp EO possesses strong insecticidal potential against cereal aphids, while its biological activity appears to be primarily associated with toxic effects rather than behavioural deterrence.