Development of a Melia azedarach L. based natural herbicide: formulation and efficacy studies

This study evaluated the phytotoxic activity of Melia azedarach L. leaf extract against Echinochloa crus-galli and Phaseolus lathyroides. Crude extracts were obtained using sequential solvent separation, of which the dichloromethane fraction exhibited the highest phytotoxicity for both weed species. However, P. lathyroides appeared more sensitive to the extracts compared to E. crus-galli. GC-MS analysis of the dichloromethane crude extract identified phytol (29.14 %), linolenic acid (21.74 %), and palmitic acid (7.20 %) as the main chemical components. Three formulations, a soluble liquid (SL), pellet, and wettable powder, were developed and evaluated for their effects on seed germination and seedling growth. The SL formulation showed the highest efficacy in inhibiting germination (p < 0.05). Further testing of its pre-emergence utility via soil application in greenhouse conditions confirmed the herbicidal efficacy, effectively suppressing P. lathyroides emergence (36.8 % over control) and reducing growth parameters. Mechanistic assays showed the SL product to affect seed imbibition, α-amylase activity, and cell division in a dose-dependent manner, suggesting these as potential mechanisms of action. This study highlights the potential of a M. azedarach-based SL product as an alternative to synthetic herbicides, potentially leading to the development of a new botanical herbicide.