Floristic diversity of weeds and herbicide use practices in rice-growing systems in the Zouan-Hounien department (Western Côte d’Ivoire)

Weeds constitute a major constraint to rice production in Côte d’Ivoire and promote increasing reliance on herbicides. This study aimed to characterize the weed flora of rice fields and to inventory the herbicides used in the Zouan-Hounien department (Western Côte d’Ivoire). Surveys were conducted with 53 rice farmers between March and June 2023, complemented by floristic surveys carried out using 4 m² quadrats. A total of 80 weed species belonged to 57 genera and 27 families, were recorded, with a predominance of Poaceae and Cyperaceae. The structure of the weed communities highlighted 29 highly aggressive species, 22 aggressive, and 29 less aggressive, dominated by Fimbristylis littoralis, Cyperus difformis, Panicum laxum, and Ludwigia abyssinica. Shannon diversity indices ranged from 3.09 to 3.68 bits, while Sørensen similarity coefficients (≥ 50%) indicated a relative floristic homogeneity between localities. Furthermore, 37 commercial herbicides were recorded, of which 23 were actually used by rice farmers, mainly glyphosate-based formulations. The most frequently used herbicides were Tête Rouge 360 SL and Herbextra 720 SL. These results highlight a high weed diversity associated with a heavy reliance on chemical control, emphasizing the need to promote integrated weed management strategies in rice cultivation.