Studies on host plants of the sweet potato weevil, Cylas formicarius (Fabricius) (Coleoptera: Brentidae) and the West Indian sweet potato weevil, Euscepes postfasciatus (Fairmaire) (Coleoptera: Curculionidae).
Field and laboratory experiments were conducted to study the infestation of the sweet potato weevil, Cylas formicarius and the West Indian sweet potato weevil, Euscepes postfasciatus on several suspected host plants in Okinawa, Japan. Both weevils infested five species of the plants belonging to family Convolvulaceae, namely Ipomoea aquatica, Ipomoea tricolor, Pharbitis nil, Quamoclit vulgalis and Q. multifida. On the other hand, the weevils did not reproduce, nor feed on Manihot esculenta, Thunbergia grandiflora, Piper retrofractum, Bidens pilosa f. decumbens, Dioscorea japonica, Dioscorea batatas and Dioscorea alata. However, the feeding behaviour on the roots of carrot, Daucus carota var. sativa was observed in the laboratory, but the infestation was not confirmed in the field experiments.