August 2017. Damage to yam in Fiji by a weevil; is it Paleopus costicollis?
It looks like Elytroteinus geophilus (Lucas, 1861) (Curculionoidea, Curculioninae, Cryptorhynchini). Known also as the Fijian Ginger Weevil, Kuschel (2008) says it is known from Cook Islands, Fiji Islands, New Caledonia, Tonga, Vanuatu, Wallis, and Western Samoa. Kuschel adds that it can be reared on taro, ginger, yam, fruits of Inocarpus edulis and adults can occasionally be found on Hibiscus and Coconuts. It can be a big problem in New Caledonia on yam stocks but rarely in the fields.
Wolfgang Gerlach in his book Plant Diseases of Western Samoa shows it associated with a collar rot of passionfruit in Samoa and it has been found in sweetpotato in the region. It is figured on PaDIL too, http://www.padil.gov.au/maf-border/pest/othernames/140305, as well as Crop Knowledge Master http://www.extento.hawaii.edu/kbase/crop/type/elytrote.htm. There is a post on Pestnet suggesting it was on sweetpotato in CMNI, but this was later corrected to Daealus tuberosus: Pests/PestsEntities/Insects/Beetles/Weevils/Daealustuberosus,CMNI
In all these, it appears under the synonym, Elytroteinus subtruncatus.
The white blotches on the elytra, the wide pronotum, and the truncate abdomen and elytral apices are diagnostic for Elytroteinus geophilus. This species has frequently been recorded as feeding on a number of different crops, including ginger, taro, lemons and sugarcane. Dioscoreaspp. have not been yet been recorded in the literature as a host plant.