Slugs are serious pests of horticulture and agricultural crops. Beside the ability of some plant growth regulators to regulate the growth of cultivated plants, they have Eco-toxicological effects on some invertebrates. So the present study was performed to evaluate the biological toxicity of sublethal concentrations (200 and 400 µl/l) of the plant growth regulator (PGR), Esrel (48% Ethephon), on Deroceras reticulatum after 2 weeks of exposure. The LC₅₀ and LC₉₀ were 980 and1500 µl/l, respectively. The obtained results indicated that PGR treatment led to a significant decrease in growth rate (P≤0.05), by the end of experiment it was 1.5 ± 0.03 g, 1.3 ± 0.04 g at the concentrations 200, and 400 µl/l, respectively compared to control (2 ± 0.03 g). In addition, flow cytometric analysis of cell cycle and immunohistochemical assays recorded DNA damage in digestive gland cells of D. reticulatum. The percentage of apoptosis was 78% and 93% at the concentration 200 and 400 µl/l, respectively, compared with control (8%). The study concluded that Esrel has toxic and apoptotic effects on D. reticulatum, so it has been proposed that the Esrel can be used as a molluscicide for the slug, Deroceras reticulatum.