Effect of Neem (Azadirachta indica) Leaf Aqueous Extract on Internode Length of Selected Cowpea Varieties Infested with Fusarium oxysporum

Cowpea (Vigna unguiculata L.) is a major grain legume cultivated extensively in sub-Saharan Africa; however, its productivity is severely limited by soil-borne fungal pathogens, particularly Fusarium oxysporum. This study evaluated the effect of neem (Azadirachta indica) leaf aqueous extract on internode length of three cowpea varieties Sampe, Pampe 12, and a local cultivar infected with F. oxysporum. A pot experiment was conducted using a completely randomized design, where infected plants were treated with neem leaf aqueous extract, while untreated infected plants served as controls. Internode length was measured at defined growth stages, and data were subjected to analysis of variance. Application of neem extract significantly enhanced internode length compared with the untreated control, indicating a reduction in the deleterious effects of Fusarium infection. Varietal responses differed, with Pampe 12 exhibiting the greatest tolerance and growth recovery following treatment. The findings demonstrate the potential of neem leaf aqueous extract as an environmentally friendly alternative to synthetic fungicides for managing Fusarium wilt and improving vegetative growth in cowpea.