The protection of new cork oak plantations against the larvae of the beetle Sphodroxia maroccana (Melolonthidae), which destroy the roots of newly planted trees, was provided for many years in the forest of Mamora in Morocco by the use of carbosulfan, usually formulated as dry granules for direct incorporation into the soil at planting. Ecotoxicological tests were conducted in the laboratory on S. maroccana and on two non-target beetle species, namely Pachychila obtusecostata and Pimelia platynota (Tenebrionidae), to measure the acute effects of carbosulfan and evaluate the potential risk associated with inappropriate practices. The mortality was measured at both 4 d and 7 d after ingestion of a known quantity of carbosulfan. The recommended dose by the manufacturer was exceeded by at least four-fold in the Mamora Forest, with obvious environmental risks. Risks were identified for wildlife when the pesticide is misused and spread on the soil around the plants.

BACKGROUNDSphodroxia maroccana Ley is a pest of cork oak crops that damages the roots of seedlings and can severely impair cork oak regeneration. Since the banning of carbosulfan and chlorpyriphos, which were widely used against the larvae of Sphodroxia maroccana because of their harmful impact on the environment, until now there has been no pesticide against these pests. Therefore, it is particularly urgent to develop highly effective insecticidal molecules with novel scaffolds. Isoxazolines are a class of insecticides that act on γ‐aminobutyric acid (GABA)‐gated chloride channel allosteric modulators. In this work, a green synthesis of novel 3,5‐disubstituted isoxazoline‐sulfonamide derivatives was achieved in water via ultrasound‐assisted four‐component reactions, and their insecticidal activities against fourth‐instar larvae of S. maroccana were evaluated.RESULTSMost of the tested compounds showed insecticidal activity compared to fluralaner as positive control and commercially available insecticide. Especially, the isoxazoline‐secondary sulfonamides containing halogens (Br and Cl) on the phenyl group attached to the isoxazoline, 6g (LC50 = 0.31 mg/mL), 6j (LC50 = 0.38 mg/mL), 6k (LC50 = 0.18 mg/mL), 6L (LC50 = 0.49 mg/mL), 6m (LC50 = 0.24 mg/mL), 6q (LC50 = 0.46 mg/mL), exhibited much higher larvicidal activity than fluralaner (LC50 = 0.99 mg/mL).CONCLUSIONNovel isoxazolines containing sulfonamide moieties were designed, synthesized and confirmed by two single‐crystal structures of 4e and 6q. Their bioassay results showed significant larvicidal activity with significant morphological changes in vivo. These results will lay the foundation for the further discovery and development of isoxazoline‐sulfonamide derivatives as novel crop protection larvicides of cork oak. © 2023 Society of Chemical Industry.