SELECTIVE INHIBITORY POTENTIAL OF YELLOW COSMOS (Cosmos sulphureus Cav.) LEAF EXTRACT ON WEEDS AND GROWTH RESPONSE OF RICE PLANTS UNDER NET HOUSE CONDITIONS

Abstract

In the context of increasing demand for environmentally friendly weed control solutions, the application of yellow cosmos (Cosmos sulphureus Cav.) (LSNV) leaf extract under net house conditions demonstrates promising potential for developing a bioherbicide. This study employed methanolic extracts from LSNV to evaluate their inhibitory effects on three common weed species (Echinochloa crus-galli, Leptochloa chinensis, Fimbristylis miliacea) as well as their impact on rice variety OM5451. The results showed that YCLE significantly suppressed weed growth depending on the application duration and concentration. At 0.96 g/mL, the height of E. crus-galli was reduced to 29.80 cm after 14 days and remained consistently low until 28 days after treatment (DAT). Both L. chinensis and F. miliacea also exhibited strong growth inhibition at concentrations ≥ 0.48 g/mL. Moreover, the fresh biomass of all three weed species decreased by 58.92% to 71.23% at 0.96 g/mL (28 DAT), accompanied by a marked reduction in relative growth rate (GR). Notably, rice plants responded positively at low concentrations. At 0.03 g/mL, OM5451 reached a height of 59.85 cm, exceeding the control. However, growth suppression was observed at higher concentrations (0.96 g/mL), indicating a dose-dependent effect. These findings suggest that YCLE has dual potential: Effective weed suppression at concentrations ≥0.24 g/mL and stimulation of rice growth at lower concentrations. This duality positions LSNV as a promising candidate for the development of selective and sustainable bioherbicides in integrated weed management systems.