Rearing the sweet potato weevil, Cylas formicarius (Fabricius) (Coleoptera: Brentidae) on an artificial diet developed for the West Indian sweet potato weevil, Euscepes postfasciatus (Fairmaire) (Coleoptera: Curculionidae)

Abstract

The sweet potato weevil, Cylas formicarius, a serious pest of sweet potato, was reared on an artificial diet originally developed for Euscepes postfasciatus, another serious pest of sweet potato. When larvae were reared individually on the diet, the rate of adult emergence was 46%. The addition of corn oil or sesame oil to this diet improved the rate of larvae reaching the prepupal stage, and enhanced the rate of adult emergence to about 60%. On the other hand, the emergence rate was about 10% when 27–30 larvae were reared in a group. More larvae died at the first instar when reared in a group than when reared individually. In group rearing, frequent physical contact among larvae caused them to die due to injury, before they bored into the diet. Successful boring into the diet seems the first step for successful adult emergence. Females of C. formicarius did not oviposit on the E. postfasciatus diet. Replacement of the sweet potato powder contained in the diet with dried periderm of sweet potato and dried stems of wild morning glory did not improve the situation, even though the females were reproductively mature. Ovarian development was not good when rearing on these artificial diets. It is necessary to develop a novel artificial diet for egg collecting on which females can develop eggs and oviposit.