Improvement of survival of the West Indian sweet potato weevil, Euscepes postfasciatus (Coleoptera: Curculionidae), by placing absorbent paper on the artificial diet after egg seeding and ensuring air permeability of the rearing tray

Abstract

A remarkable reduction of the post-hatching survival rate caused by adopting the furcellaran solution (a viscous liquid, hereafter FS) as an egg-seeding agent has become a problem during development of mass-rearing methods for the West Indian sweet potato weevil (Euscepes postfasciatus) using an artificial diet. We hypothesized that FS physically inhibits the feeding of hatched larvae on the diet, and predicted that removing and/or drying FS after egg seeding would improve the survival of E. postfasciatus. To confirm this prediction, we examined the effects of two post-egg-seeding treatments (placing absorbent paper on the diet surface and ensuring air permeability of the rearing tray) on the survival and development of the weevils. Neither of the two treatments worked well individually, but they exhibited a clear synergistic positive effect on weevil survival. Their survival rate jumped from 2% to 40% when these two treatments were combined, without any adverse effects on the developmental period and the adult body size. These treatments thus enabled the FS-based egg-seeding method, which is much simpler than previous methods, clearly contributing to the establishment of a mass-rearing system for E. postfasciatus.