Interaction of malathion with diluents in wettable powder formulations evaluated against Sitophilus oryzae Linn. infesting stored maize

The interaction of malathion with clay diluents of different structural configurations was studied. The various formulations were prepared singly/mixture of two different diluents and with two surfactants or emulsifiers, viz, Lissapol-D and HYOXYD AAO and kept under varying storage conditions for evaluation against Sitophilus oryzae Linn. reared on stored maize. Malathion WP formulated with bento-diatomite and Lissapol-D, anionic wetting agent proved to be the most effective formulation during various storage periods, viz, freshly prepared, long term storage for twelve months and accelarated storage at elevated temperature (54±1°C) under uniform pressure of 25 gml cm² for 24 hours. With the change of wetting agent, fuller's earth deativated based WP formulated with HYOXYD AAO, non-ionic wetting agent proved to be superior to other mixture of diluents based WP formulations in different periods of storage. HYOXYD AAO seemed to act as deactivator of active sites of fuller's earth from the experimental evidence as no significant difference was found between deactivated and plain fuller's earth. In all the formulations, the effect of physical mixture of two diluents was not pronounced as evident due to less variation in eflicacy between the most effective and least effective formulations. The bioeflicacy of formulations was interpreted in the light of physicochemical properties based on mineralogical characterization of clay diluents as revealed by x-ray diffraction analysis and chemical composition of the diluents.