The effects of two neonicotinoids at three application rates (0, 2.5 and 5.0 ml kg^-1 seed for thiamethoxam, and 0, 2.0, 4.0 g kg^-1 seed for imidacloprid) and two methods of breaking dormancy (dry heat treatment and operculum removal) on seed germination and seedling vigour were determined in tenera oil palm seeds. The results reveal that the seeds with operculum removed took a shorter time to germinate than the dry-heated seeds, regardless of the neonicotinoid treatments. Thiamethoxam and imidacloprid had no promoting effects on seed germination or on time to 50% germination (T₅₀). In this study, phytotoxicity effects were observed with the neonicotinoid treatments in the operculum-removed seeds in terms of the percentage of seeds producing shoots and roots as compared to the normal seedlings (control); such effects were not found in the dry-heated seeds.

Keywords: dormancy, germination, imidacloprid, oil palm seed, Thiamethoxam