ENHANCING THE POTENCY OF VEGETABLE OILS BY COMBINING WITH PIRIMIPHOS~METHYL FOR PROTECTION OF STORED COWPEA AGAINST INFESTATlON BY CALLOSOBRUCHUS MACULATUS (FAB.)

Abstract

The cowpea beetle Callosobruchus maculatus (Fab.) is a major insect pest of stored cowpea in Ghana. The efficacy of coconut, groundnut and
soybean oils applied at 1, 2, 5 and 10 ml kg-! and pirimiphos-metltyl at 2.5, 5.0 and 1.0 ",I active ingredient in 2 ml of water kg-I of grain (1116, 118 and 1/4 of the recommended dose) alone or in combination to adults and immature stages of C. maculatus and the persistence of the treatments in cowpea grain were evaluated in the laboratory. All the treatments caused significant mortality compared to untreated controls. Lower dosages of the oils and pirimiphos-metbyl when combined were highly toxic to C. maculatus. The mixtures also completely inhibited the development of immature stages of the beetle. Only pirimipbosmethyl
and the mixtures remained effective 60 days after application. Pirimipbosmethyl can be used at reduced rates if combined with lower dosages of vegetable oils to control the infestation of C. maculattlS in stored cowpea.