Organic mulch as a potential management option for sweet potato weevil (Cylas puncticollis) in sweet potato production

Sweet potato farmers in Nigeria faced the challenge of heightened infestation of the roots by C. puncticollis particularly in the dry season. During this season, soil cracks facilitate the weevil entry, which tunnels into the roots and decreases its quality and market value. Mulch contributes to pest suppression in crops by producing volatile compounds, making pest accessibility challenging. In this study, the potentials of four organic mulches were explored in the management of C. puncticollis. The experimental design was completely randomized with two blocks (covered and uncovered) each comprising four categories and a control. Manures (poultry and cow dung), wooden materials (sawdust and wood chips), plant materials, (Ocimum gratissimum and Lantana camara), and plant wastes (oil palm bunch refuse and oil palm fiber) were screened in a multi-choice mesocosms against C. puncticollis. In the uncovered experiment, the potato roots were left exposed to simulate cracked field soil. For the covered experiment, the roots were covered with 2 cm of soil, mimicking field conditions where soil remains over developing storage roots. Results showed that for the covered-manure mulch, feeding punctures counted on poultry manure (1.5) and cow dung (2.0) treated roots were significantly lower than the control (3.8). For the uncovered-manure mulch, a significantly lower number of feeding punctures (7.1 and 7.7) were observed on poultry manure and cow dung-treated roots compared to the control (11.5). Overall, lower numbers of feeding punctures and weevils were observed in the mulch-treated roots compared with the control. It is recommended that mulching with organic materials can be an effective strategy in the integrated management of sweet potato weevil, particularly during dry periods when soil cracking can facilitate pest access to the storage roots.