Planthoppers and leafhoppers are key rice pests in paddy fields. This study aimed i) to evaluate the occurrence of these pests in paddy fields using nursery box-applied granules containing the conventional insecticide imidacloprid or the novel insecticide triflumezopyrim, and ii) to examine the indigenous natural enemies of these insects in organic paddy fields. We investigated the occurrence of planthoppers, leafhoppers, and their indigenous natural enemies in six conventionally (i.e., chemically) controlled and three organically cultivated paddy fields under commercial production in Shizuoka Prefecture, Japan, in 2021. Paddy fields where triflumezopyrim-containing granules were applied to nursery boxes tended to show lower planthopper densities than fields where granules containing imidacloprid were used in nursery boxes. The density of leafhoppers did not show a clear difference between the two chemicals. The results suggest that triflumezopyrim applied to nursery boxes is more effective in controlling planthoppers than imidacloprid, although further confirmation is required in years of high pest abundance. Indigenous natural enemies of planthoppers and leafhoppers occurred in both conventionally controlled and organically cultivated paddy fields. However, the occurrence of spiders (Lycosidae spp. and Tetragnathidae spp.) and planthoppers parasitized by Dryinudae spp. or Strepsiptera spp. appeared to be higher in the organic fields than in the conventional fields. Long-term surveys considering annual fluctuations in pest abundance are necessary, and the contribution of these indigenous natural enemies in suppressing planthopper and leafhopper densities must be verified.
