Comparative bioactivity of three Khaya species (Meliaceae) against Callosobruchus maculatus Fabricius (Coleoptera: Bruchidae)

Abstract

The efficacies of crude extracts of the stem bark of Khaya grandifoliola; K. senegalensis and K. nyasica (Meliaceae), collected within the same Nigerian ecological zone, at 0, 250, 500 and 1000 ppm were investigated as cowpea protectants against Cowpea bruchid (Callosobruchus maculatus Fabricius) under laboratory conditions at 27 + 2 oC temperature and 77 + 8% relative humidity. All Khaya extracts at 250 -1000ppm significantly reduced the oviposition of C. maculatus in treated cowpea seeds. Seeds treated with extract of K. grandifoliola had the least mean number of eggs (75.5) laid on them compared with the control (310.00). Similarly, all Khaya extracts at 500-1000ppm caused significant reduction in reproductive efficiency of C. maculatus, and the lowest significant reproductive efficiency (47.9%) was recorded in extract of K. grandifoliola at 1000ppm concentration. When topically applied, significant mortalities in cowpea bruchid adults were observed at 1000ppm concentration of K. grandifoliola and K. nyasica extracts. The body weight of emerged F1 adults from seeds treated with the three Khaya species were not found to be significantly different.