Unveiling the bioherbicidal potential of Eupatorium capillifolium (Lam.) Small for selective management of agricultural weeds

The global rise of herbicide-resistant weeds underscores the urgent need for sustainable weed management strategies. Eupatorium capillifolium (Lam.) Small, a perennial invasive weed native to North America and widespread in the Southeastern United States, presents untapped potential as a bioherbicide. This study evaluated the effects of its aqueous extract on seed germination and early seedling growth of thirteen weed species (nine broadleaf and four grasses) and four major crops (Arachis hypogaea, Zea mays, Glycine max, and Gossypium hirsutum). The extract significantly inhibited seed germination (92.62-100%) of four Amaranthus species (A. palmeri, A. tuberculatus, A. retroflexus, and A. hybridus) with minimal effects on Zea mays and Arachis hypogaea (6.12-6.25%). Other weeds showed a limited response. Inhibition of shoot and root growth confirmed the extract's allelopathic activity. Principal component analysis indicated inhibition of seed germination as the primary mode of action. The order of pigweeds' sensitivity to the aqueous extract was A. hybridus > A. retroflexus > A. palmeri > A. tuberculatus. Phytochemical screening identified 36 allelopathic compounds with gallic acid and hydroxy-1,4-benzoquinone as the dominant components. This is the first report demonstrating the bioherbicidal potential of E. capillifolium aqueous extract against Amaranthus spp. under laboratory conditions, highlighting its promise as a sustainable alternative to synthetic herbicides and a candidate for further field-based evaluation in integrated weed management systems.