Comparative laboratory and field assessment of commercial and nanoformulated metaldehyde baits against Monacha obstructa

Abstract Metaldehyde is a widely used molluscicide for controlling land snails; however, reformulation of commercial molluscicides using nanoscale delivery systems may provide an alternative approach for modifying their biological performance. This study aimed to prepare and characterize a nanoformulation of the commercial metaldehyde bait and compare its molluscicidal performance with Gastrotox 5% against Monacha obstructa under laboratory and field conditions. Laboratory toxicity was evaluated using the toxic bait method at five concentrations (1, 2, 5, 8, and 10%) for 72 h. Alkaline Phosphatase (ALP) and Acid Phosphatase (ACP) activities were determined as biochemical indicators of physiological responses, and field performance was assessed based on population reduction percentages over a 21-day experimental period. The prepared nanoformulation exhibited favorable physicochemical characteristics, with spherical particles measuring 7.4–33.5 nm, a mean particle size of 44.06 ± 4.57 nm, a Polydispersity Index (PDI) of 0.40, and a zeta potential of − 27 ± 3.24 mV. The nanoformulation showed a lower numerical LC 50 value than Gastrotox 5% (1.60% and 2.80%, respectively); however, the overlap of the corresponding 95% confidence limits did not support a statistically significant difference between the two formulations. ALP activity differed significantly among treatments, with the highest activity recorded in the Gastrotox-treated group, whereas ACP activity showed no significant differences. Under field conditions, the nanoformulation showed higher population reduction than Gastrotox 5% at all assessment times, with values of (48.55 ± 6.33%), (90.39 ± 2.95%), and (96.90 ± 3.26%) after 7, 14, and 21 days, respectively, compared with (37.14 ± 12.10%), (74.14 ± 2.30%), and (83.73 ± 11.51%) for Gastrotox 5%, respectively. The difference between the two treatments was statistically significant only after 14 days ( P ≤ 0.05). The prepared nanoformulation showed molluscicidal activity comparable to Gastrotox 5% under laboratory conditions, with a numerically lower LC 50 that was not statistically different from that of the commercial formulation. Under field conditions, the nanoformulation produced numerically higher population reduction than Gastrotox 5%, with a statistically significant advantage observed after 14 days. The differential ALP response, together with the unchanged ACP activity, indicated different biochemical responses to the two formulations. Overall, the findings indicate that the prepared nanoformulation has potential as an alternative formulation of commercial metaldehyde bait for the management of M. obstructa under the evaluated experimental conditions.