Lethality of single, binary and ternary combinations of rice husk ash, groundnut pod shell ash and Eugenia aromatica Baill powder to adults of Callosobruchus species attacking stored grain legumes

Abstract

The study investigated the lethality of powders made from rice husk ash, dry flower buds of Eugenia aromatica (L.) Baill. and groundnut pod shell ash, to adults of Callosobruchus maculatus Fabricius and C. chinensis Linnaeus at 25 ° C and 65% relative humidity. The powders were tested singly, and in binary, and ternary combinations at the dosages of 0.05, 0.1 and 0.2 g/10 g of grain in glass Petri dishes. The powder combinations were mixed in equal proportions. There was a control involving no powder. Adult mortality of 20 individuals was observed 24, 48 and 72 h post treatment. Data analysis indicated significant differences among treatment means. Adult mortality increased with increase in dosage of powders and period of exposure. When applied singly the three insecticidal powders showed decreasing lethality to the adults beetles in this order E. aromatica > rice husk ash > groundnut pod shell ash. In the binary and ternary combinations with equal proportion of materials, the less toxic powders were significantly enhanced in lethality. The use of the binary and ternary combinations may be favoured for use in mitigating Callosobruchus damage to stored grain legumes for reasons of affordability, sustainability and durability.