Integrating Variety, Land Configuration and Fertility Management for Sustainable Management of Cylas Weevil Infestation in Sweet Potato Under Degraded Savanna Alfisols

The sweet potato weevil (Cylas spp.) is a major constraint to sweet potato production, yet the effectiveness of integrated agronomic approaches for its management remains insufficiently understood in the Nigerian savanna. A three-year field experiment (2023–2025) at the University of Abuja Teaching and Research Farm evaluated the effects and interactions of variety, land configuration, and fertilizer source on Cylas infestation, root quality, and marketable yield. Two varieties, orange-fleshed (OF) UMUSP3 and white-fleshed (WF) TIS-87/0087, were evaluated under flat, mound, and ridge configurations combined with NPK 15:15:15, poultry manure, Hyptis suaveolens green manure, and an unfertilized control in a factorial randomized complete block design with three replications. Variety significantly affected Cylas infestation, with OF recording 10.79 infected roots/plot compared with 8.28 roots/plot in WF, whereas land configuration alone had no significant effect. Fertilizer management strongly influenced infestation and root quality, with green manure recording the lowest Cylas incidence (3.61 roots/plot) and unmarketable roots (6.20 roots/plot), compared with 15.50 and 23.11 roots/plot, respectively, under the control. Significant variety × fertilizer and land configuration × fertilizer interactions indicated context-dependent responses. Cylas infestation was negatively correlated with marketable yield (r = −0.301) and fresh biomass (r = −0.201), indicating that increasing infestation was associated with reduced productivity. Integrating suitable varieties, organic nutrient management, and complementary land configurations can strengthen Cylas management, reduce weevil-associated losses, and sustain sweet potato productivity under savanna conditions.