Abstract
In this study, the efficacy of two entomopathogenic nematodes species against the potato weevil, Cylas formicarius, a serious pest of sweet potato in Sri Lanka was evaluated. In the laboratory, Heterorhabditis megidis produced 80-90% mortality of larvae, pupae and adults while Steinernema feltiae produced 70-80% mortality. In a small plot experiment under field conditions also showed significant insecticidal efficacy on the weevil thereby reducing damage to local sweet potato varieties, CARI-426, CARI-426-13. Although carbofuran gave a considable reduction in damage by the weevil, the degree of control was significantly less than those of two nematode species. A field experiment conducted in large pots with thevariety, 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 potential of two entomopathogenic nematode species showed a possibility of biological control measure against sweet potato weevil in Sri Lanka.
