Sweet Potato Weevil

📖 Description

Sweet Potato Weevil (Cylas formicarius) is the most destructive pest of sweet potato worldwide and the single biggest constraint to sweet potato production across the Indian subcontinent, particularly severe in Odisha, Bihar, Jharkhand, West Bengal, Uttar Pradesh, Assam and Tamil Nadu where sweet potato is grown on over 130,000 hectares. The weevil is unusual in having a markedly ant-like appearance (orange-red head and thorax, dark blue-black elytra, elongated snout) — this ‘formicarius’ (ant-like) resemblance provides some protection from predators through mimicry. Both adults and larvae damage the crop — adults feed on vines and leaves, while larvae bore into tubers and vines, causing characteristic tunnelled damage with frass. The pest also induces production of toxic terpenoids in infested tubers — these compounds give infested tubers a bitter taste and can cause illness if consumed, making infested tubers unsafe for both human and livestock consumption. IPM with pest-free vine cuttings (the single most important preventive measure — most new infestations originate from infested planting material), sex pheromone traps for mass trapping of males (one of the most successful IPM programs in tropical root crops), Beauveria bassiana soil applications, early harvest, and removal of infested plants provides effective and sustainable control. The pest is most severe in continuous sweet potato cultivation and in areas where wild Ipomoea hosts serve as reservoirs between cropping cycles.