Sweet potato weevil

Palaeopus subgranulatus is a coleopteran insect belonging to the Curculionidae family. This pest is recognized as a significant threat to tropical root crop production, specifically targeting sweet potatoes (Ipomoea batatas) and causing severe yield losses in endemic cultivation regions.

The primary diet of this pest consists of sweet potato tubers. Both adult weevils and larvae develop within the tuber tissue, excavating extensive tunnels. This feeding behavior destroys the marketable quality of the crop and renders the tubers unsuitable for consumption, often triggering secondary infections by fungi and bacteria.

The biological life cycle of this weevil is intimately linked to its host plant. Females deposit eggs directly into the skin of the tuber or the underground stems. The emerging larvae burrow into the flesh, feeding and progressing through larval instars until pupation, which occurs within the tuber itself, thereby completing the cycle protected from external environment.

Damage symptoms are identifiable during harvest: the tuber surface exhibits small entry holes, often accompanied by frass-filled tunnels internally. Severe infestations cause the tubers to produce bitter compounds and emit foul odors as a chemical defense mechanism, making the crop completely unpalatable and unmarketable.

Management strategies require a multidisciplinary approach focused on sanitation and cultural control methods:

• Utilizing certified pest-free propagation material for planting.
• Implementing strict crop rotation cycles and spatial isolation of new plantations.
• Eliminating wild host plants, particularly related Convolvulaceae weeds.
• Scheduling early harvests to minimize the exposure time of tubers to infestation in the soil.
• Deploying biological control agents or targeted insecticides when pest pressure thresholds are exceeded.