Residues of pirimiphos-methyl in stored maize grains

14C-pirimiphos-methyl (specific activity 16.36 mCi/mmol (1 Ci = 37 GBq)) was applied to maize grains at a concentration of 5 mg/kg using the procedures described in the FAO/IAEA Model Protocol, Annex I, these Proceedings. After treatment, the maize was stored at ambient temperature (20-35 deg. C) in jute sacks lined with polythene. The surface (water soluble) and methanol extractable residues were investigated over a period of 8 months. There was a gradual increase in the methanol extractable residues and a corresponding decrease in the surface residues over the storage period. At the end of this time, the total extractable residue was 56% of the applied dose. For technical reasons no data were available for the residues bound within the grain tissues. Four types of local diet were prepared from the treated maize, these being: akple, roasted akple, kenkey and banku; some reduction in the extractable residues was observed as a result of the cooking process. (author)