Potential of Entomopathogenic Nematodes as Bio-Control Agents of Sweet Potato Weevil, Cylas formicarius (FABRICIUS)(Coleoptera: Brenthidae)

Abstract

In this study, the efficacy of two entomopathogenic nematodes species (Heterorhabditis megidis and Steinernema feltiae) against the potato weevil, C. formicarius, a serious pest of sweet potato in Sri Lanka, was evaluated. In the laboratory, H. megidis produced 80-90% mortality of larvae, pupae and adults while S. feltiae produced 70-80% mortality. A small plot experiment under field conditions also showed significant insecticidal efficacy of the nematodes on the weevil thereby reducing damage to local sweet potato cultivars CARI-426 and CARI-426-13. Although carbofuran gave a considerable reduction in crop damage by the weevil, the degree of control was significantly less than those of the two nematode species. A field experiment conducted in large pots using cv. Wariyapola Red, showed low levels of weevil control due to S. feltiae or carbofuran. However, H. megidis produced significantly higher levels of weevil control than S. feltiae or the chemical. Results of the experiments on the potential of the two entomopathogenic nematode species showed a possibility of biological control measure against sweet potato weevil in Sri Lanka.