Abstract

The effectiveness of five plant species (Nicotiana tabacum L., Hyptis sauvolens Poit, Ocimum gratissimum L., Cymbopogon citrtus Stapf and Lantana camara L.) were investigated using their leaf powders at 0, 5, 10, 15 and 20 g w/w as protectants of kolanuts against weevils. Nicotiana tabacum and C. citrtus suppressed the rate of Balanogastris kolae development at the treatment level of 15 g with mean adult emergence of 4.71 and 5.21, respectively, which differed significantly (p<0.05) from their control treatment (19.46). The various treatments of all the powder at 10 g treatment level (0.21 to 0.29) significantly (p<0.05) suppressed the rate of Sophrorhinus species development and emergence from the stored kolanuts. At the highest treatment levels of 20 g, there was no significance difference (p>0.05) between the control treatment mean colour change of 0.58 when compared with values recorded for H. sauvolens (0.58), O. gratissimum (1.17), C. citrtus (0.96) and L. camara (0.83). The mean number of exit holes found on the kolanuts decreased with increased concentrations of the various powder treatment levels 5 g (17.0 to 32.0), 10 g (13.21 to 28.83), 15 g (8.17 to 17.67) and 20 g (6.5 to 10.5). The plant powders did not impart any undesirable quality on the nuts.

Key words: Kolanuts, weevils, development, emergence, treatments.