Laboratory assessment of Lantana camara L. extracts for selective inhibition of rice weeds: phytotoxicity, crop response, and phenolic composition.

Abstract

Weeds significantly reduce rice (Oryza sativa L.) yield and grain quality, highlighting the need for sustainable weed management strategies. This study evaluated the bioherbicidal potential of methanolic extracts from Lantana camara L. (LC) against dominant rice field weeds Echinochloa crus-galli (BY), Leptochloa chinensis (RS), and Fimbristylis miliacea (GF), and examined the recovery responses of rice varieties OM18 and OM5451. At 0.48 g/mL, LC extract markedly suppressed shoot and root growth in RS, and GF, with root inhibition reaching 95.14-100%. BY was less sensitive, especially in shoot growth (24.21% inhibition). Interestingly, low concentrations (0.01-0.06 g/mL) promoted early rice growth, suggesting hormetic stimulation. IC₉₀ values confirmed differential sensitivity: GF was most susceptible (0.129 g/mL), while BY was highly resistant (2.658 g/mL). OM5451 showed greater recovery after 168 h. HPLC analysis identified major phenolic compounds as veratric acid (5.605 µg/mL), p-coumaric acid (1.533 µg/mL), vanillic, salicylic, and gallic acids likely contributing to LC's phytotoxicity. While the findings underscore that LC may be potent as a selective natural herbicide, this laboratory-based study remains exploratory. Field-scale validation, ecological impact assessments, and formulation refinement are essential next steps. Nevertheless, this work highlights LC's dual role, as both an invasive species and a possible bioresource for eco-friendly weed control.