Synergism of Entomopathogenic Nematode and Imidacloprid: A Curative Tool to Coconut white Grub,Leucopholis coniophora(Coloeptera: Melolonthinae)

Abstract

Insecticide imidacloprid and entomopathogenic nematode (EPN), Heterorhabditis indica alone and in combinations of imidacloprid and EPN were evaluated against early and late 3rd instars of coconut white grub, Leucopholis 3rd coniophora. Field collected instars white grubs were placed in pots with sweet potato treated with imidacloprid, the EPN, or both. In all nematode-imidacloprid combinations, both early and late 3rd instars grub mortality was significantly higher than in the H. indica alone and imidacloprid alone treatments. Combinations of imidacloprid and nematodes had a strong synergistic effect on mortality at different concentrations of imidacloprid. Nematodes were admixed with various concentrations of imidacloprid ranging from 0.04 to 1.25% could not significantly affect the survival of infective juveniles resulting in only a negligible mortality (3.5%). Results revealed that different imidacloprid concentrations, exposure time and interaction between imidacloprid and exposure time not affected nematodes mortality in bioassay. Combinations of imidacloprid and entomopathogenic nematodes may provide a powerful and economically feasible curative control in white grub management in coconut.