Effects of Formulation and Treatment Method of Imidacloprid in Nursery Boxes on Aquatic Insects Inhabiting Rice Paddy Fields

The abundance of larvae of midge and mayfly, Cloeon dipterum (Linnaeus), in paddy plots with conventional release granular formulation corresponding to before transplanting treatment in nursery boxes (BT treatment), was significantly lower than in control plots 14 days after transplanting (DAT), but species abundance in BT plots was significantly higher than in control plots at 28 DAT. On the other hand, there were no significant differences in the abundance of aquatic insects, including midge and mayfly larvae, in paddy plots with controlled release granular formulation, corresponding to at sowing treatment in nursery boxes (AS treatment), and control plots at 14 and 28 DAT. Moreover, for introduced nymphs of ferocious water bug, Appasus japonicas Vuillefroy, paralysis occurred in greater frequency in BT plots than in AS plots.