General Information

Sweet potato weevil
Scientific name: Cylas formicarius
Coleoptera:Curculionidae

Other species

1. African sweet potato weevil (Cylas puncticollis) is found only in sub-Saharan Africa.
2. West Indian sweet potato weevil (Euscepis postfasciatus) is found in the Caribbean and several island countries in the Pacific.

Hosts

Sweet potato, its alternate hosts are morning glory and water spinach but it will also feed on other Ipomea weeds

Distribution

Sweet potato weevil is found worldwide

Damage

The larva prefers to feed on the tuber. An infested tuber is often riddled with cavities as a result of its tunneling activities. It becomes spongy, brownish to blackish in appearance, and has a bitter taste and foul odor. But before tuber formation, it feeds on the vine. A damaged vine is discolored, cracked, or wilted.

Description

The egg is laid singly in small cavities on the sweet potato root or vine tissues that is nicely sealed with the mother's fecal material. It is ovate-shaped and creamy-white in color. It is about 0.7 mm in length and 0.5 mm in width.. It hatches in about 5-6 days.

The larva is legless and white in color. It is found feeding on the vine near the base of the plant and goes down to the roots to feed on the tuber. It can reach a length of 0.78 mm. It will undergo 3 larval stages which will last for about 35-56 days depending upon the climatic conditions.

The pupa is white and turns grayish with darker eyes and legs as it further develops. It looks similar to the adult but its head and elytra are bent ventrally. It measures about 6.5 mm in length. The pupal stage lasts for about 7-28 days.

The adult has a black head, orange to reddish-brown antennae, thorax, and legs, and a metallic-blue abdomen and elytra. Its body, legs, and head are long and thin, giving it an ant-liked appearance. It measures 5.5 - 8.0 mm in length.