Process optimization and field performance of semi-synthesized methyl eugenol for Tephritidae fruit flies management

The Tephritidae fruit flies, particularly polyphagous Bactrocera species, cause severe economic losses in fruit production across tropical and subtropical regions. Methyl eugenol (ME) is a key semiochemical attractant used in male annihilation technique (MAT) traps for monitoring and managing these pests. Ensuring accessible high-purity ME from sustainable sources could reduce dependence on broad-spectrum insecticides. In this study, ME was semi-synthesized from natural eugenol via O-methylation using dimethyl sulfate (DMS). The process was optimized using a Box-Behnken design (BBD)-based response surface methodology (RSM), with reaction temperature, time, and DMS-to-eugenol molar ratio as independent variables. The synthesized ME was field-evaluated as a trap lure using dose-response bioassays.

Optimal synthesis conditions were 110 °C, 24 h, and a 1.736 molar ratio of DMS to eugenol, achieving a chromatographic peak area of 97.97% (desirability = 0.981), and yielding 19.78 g (90.98% isolated yield) of high-purity ME (> 98%). Field bioassays revealed a significant dose-dependent attraction of Bactrocera spp. (confirmed as Bactrocera dorsalis, Bactrocera carambolae, Bactrocera correcta, and Bactrocera zonata). Traps baited with 1.5 mL of synthesized ME lure captured significantly more flies than lower doses (19.51 ± 0.42 flies per trap per day; relative efficiency 38.93 ± 0.18%), approaching the performance of 1.0 mL commercial ME (38.39 ± 0.32%). The 1.5-fold higher dose requirement relative to the commercial ME control is discussed in the context of formulation matrix and release-rate differences.

Semi-synthesized ME from natural eugenol purity and field efficacy was suitable for use as a MAT-trap lure in Bactrocera species monitoring programs. The dose-dependent trap performance, coupled with the scalable green-chemistry synthesis route, supports ME's role in integrated pest management. Application within enclosed dispensers with appropriate worker safety protocols is recommended, in line with regulatory guidance on ME use in agriculture. © 2026 Society of Chemical Industry.