Allelopathic effects of aqueous leaf extracts of five invasive species in Côte d'Ivoire on maize (Zea mays) and rice (Oryza sativa)

Chromolaena odorata, Euphorbia heterophylla, Fleischmannia microstemon, Porophyllum ruderale and Synedrella nodiflora are five invasive plants in agrosystems in Côte d'Ivoire. They strongly influence the structure and diversity of native plant communities. In addition, they can compete for water and nutritional resources with cultivated plants, leading to a decrease in agricultural yield. This competition often occurs through the emission of allelochemicals that prevent seed germination or inhibit the development of other species. Thus, this study aims to assess the allelopathic effects of these five species on maize and rice, two crops generally used in food self-sufficiency programmes. To this end, the seed germination, root and stem growth of these crops watered with different leaf extracts of these five species were monitored in the laboratory. All five species were found to have allelopathic effects on maize and rice development. However, the action of the allelochemicals is specific to the target plant organs and increases with the concentration of the extracts. The study shows that of the five plants, C. odorata, E. heterophylla and F. microstemon are the most damaging as they have a more pronounced effect on seed germination.