Enhancing the potency of vegetable oils by combining with pirimiphos-methyl for protection of stored cowpea against infestation 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-1 and pirimiphos-methyl at 2.5, 5.0 and 10 ml active ingredient in 2 ml of water kg-1 of grain (1/16, 1/8 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-methyl when combined were highly toxic to C. maculatus. The mixtures also completely inhibited the development of immature stages of the beetle. Only pirimiphos-methyl and the mixtures remained effective 60 days after application. Pirimiphos-methyl can be used at reduced rates if combined with lower dosages of vegetable oils to control the infestation of C. maculatus in stored cowpea.

SINET: Ethiopian Journal of Science Vol. 23, No. 2 (December 2000), pp. 263-272




Key words/phrases: Callosobruchus maculatus, cowpea, mortality, pirimiphos-methyl, potency