A simple procedure has been developed for estimating the amount of the paddy pesticides used with each application method. We analyzed the usage for 14 insecticides used in Japanese paddy fields. Insecticide application was classified into five methods: ground application in paddy fields, nursery box application in paddy fields, aerial application in paddy fields, application in fields and orchards, and other applications. Based on the application method for each target pest provided in the pesticide application list, the fraction of usage with each application method was calculated, assuming that the usage was evenly distributed to each target pest. The usage with each application method in each prefecture was then calculated by multiplying the total usage by the fraction of usage for each application method. The accuracy of estimated usage in paddy fields was validated by a comparison with the estimated insecticide emission in paddy fields reported by the Pollutant Release and Transfer Register (PRTR) system. Estimation errors were largely around twofold; therefore, their accuracy would be similar. However, the errors became large when the usage amounts in paddy fields of each prefecture were small.
The effects of processing and cooking on the residue levels of benomyl, which was applied preharvest and determined to be as carbendazim, were investigated. In the case of edamame, the residual amount ratios (%, RARs) in raw seeds as the edible portions were reduced to 1% after removing the pods. Although more than 70% of the initial residues were eliminated into the boiling wastewater, the RARs in boiled seeds slightly increased to 2.6–3.6%. This increase indicated that a part of the residue was translated from the pod to the seed portion during the boiling process. In the case of wheat, the RAR of flour as the major edible portion was 26% after the milling process. However, the process of cooking wheat flour, such as making bread and lumping noodles, caused no significant reducing of RARs. Removing edamame pods and milling wheat effectively reduce benomyl residue.