Degradation of malathion as a function of grain drying systems
1992
Wintersteen, W.K. | Foster, D.E.
The effect of grain drying and grain storage temperatures on degradation of dust and emulsifiable concentrate formulations of malathion was examined. Malathion was applied before drying on wet corn (19-20% moisture content) or after drying on either hot (71 or 48 degrees C) or cool (21 degrees C) corn (12% moisture content). All treatments were dried to a final moisture content of 12% under three drying temperatures: 21, 48, and 71 degrees C. Storage temperature effects were evaluated for all treatments with corn stored at 3 degrees C for 4 mo, followed by storage at 16 degrees C for 7 mo. Malathion applied before drying was significantly degraded by the drying process, and degradation was dependent on drying temperature and formulation. Degradation during 3 degrees C storage was negligible, but during 16 degrees C storage, malathion applied before drying on corn that was then dried at 48 or 71 degrees C had a significantly lower rate of degradation than grain dried at 21 degrees C. Despite these differences, bioassay results with adults of the rice weevil, Sitophilus oryzae (L.), and the red flour beetle, Tribolium castaneum (Herbst), showed that biologically active residues were present throughout the entire storage period, indicating that either malathion formulation is effective when applied immediately before or after drying at a wide range of temperatures.
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