| Abstract: | The biological activity of freshly-applied fenitrothion on maize at a range of moisture contents was measured using adults of several species of Coleoptera. Activity declined by about ×15 as grain moisture increased from 10 to 24%, the greatest change occurring at moisture contents above about 14%. This occurred regardless of whether the grain was treated with fenitrothion when already moist or was moistened after treatment, and it was not reversed by drying the treated grain. These differences in activity could not be explained by differences in the chemical residues. The suggested mechanism is a reduction in the availability of fenitrothion for pick-up by insects. |
