Comparative effect of grain moisture on the biological activity of protectants on stored corn
1988
Samson, P.R. | Parker, R.J. | Jones, Al
Increasing moisture content of corn had the same adverse effect on biological activity of fenitrothion formulated as an emulsifiable concentrate (EC), wettable powder, or dust against Tribolium castaneum (Herbst). The proportion of residues of the three formulations extracted by a surface wash withmethanol was also reduced in similar proportions as moisture content increased. Among five organophosphorus compounds (all EC) tested against T. castaneum, fenitrothion was the most adversely affected by moisture content (14 and 18%) and chlorpyrifus-methyl the least, and all were more affected than the pyrethroid deltamethrin (EC). Against Rhyzopertha dominica (F.), biological activities of methacrifos and carbaryl (water-dispersed colloid) were much reduced at higher moisture content, while the activities of five pyrethroids (EC or miscible oil) were slightly reduced. Over a greater range of moisture contents, activities of fenitrothion, chlorpyrifos-methyl, and pirimiphosmethyl agaisnt T. castaneum were substantially reduced only above acorresponding equilibrium relative humidity of 70-80%. No such threshold was measured for carbaryl, an increase in moisture having considerable effect on activity even when grain was quite dry. Effect of moisture on activity of deltamethrinwas significant but relatively small, particularly against T. castaneum.
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