Chemical composition and insecticidal effect of fruit peel powders of two citrus species against Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) in stored cowpea (Vigna unguiculata)

Citrus which belong to family Rutaceae is one of the most important commercial crops with a growing demand. Outer peel of Citrus fruits of several species is known to possess oil with some insecticidal properties. The one year study was thus carried out to evaluate the repellent and toxic effects of the fruit peel powder of Citrus nobilis and Citrus medica against pulse beetle, Callosobruchus maculatus. Increasing repellent activity against insects was observed with increasing dose for both plants where the highest repellency was elicited by C. nobilis. Significant reduction in oviposition, egg hatchability and adult emergence were observed in both Citrus species. Moreover, no significant effects were observed on seed viability and consumer acceptability between control and treatments. Chemical constituent characterization revealed, d-Limonene to be the major constituent of both C. nobilis (45.3%) and C. medica (68.3%) plant species. Overall results indicate high potential of both Citrus species, particularly C. nobilis as a repellent, toxicant and growth inhibitor to reduce the damage caused to leguminous crops by C. maculatus.