Stability of organophosphate and pyrethroid pesticides on wheat in storage

The pesticides chlorpyriphos-methyl, pirimiphos-methyl and permethrin were applied to wheat and stored for 52 weeks at 25, 30, 35 and 40 degrees C, and at 10 and 13% m.c. Rates of loss were calculated from the residue analyses of pesticides in treated wheat at monthly intervals during the storage period. Calculated half-lives and pseudo first-order rate constants of these pesticides are discussed with reference to temperature and moisture.