Toxicity of Ocimum suave (Wild basil) crude oil extract on C. maculatus and test on seeds’ viability, was determined in the laboratory using contact toxicity assay method of different concentration 0.02, 0.04, 0.06 and 0.08mg to 20ml of water and 0.00g/20ml of water (control). 20g of cowpea seeds were weighed into separate Petri dishes and 10 adult weevils were inoculated and replicated four times. Each treatment was observed for 96h and recorded after every 12h. The result indicated that the crude oil extract had significant difference (p0.05) in the germination of treated cowpea seeds (Vigna unguiculata L) compared to the untreated control, which shows that the seeds still remained viable. This result showed that O. suave crude oil is effective in the protection of cowpea against cowpea bruchid Callosobruchus maculatus.
Background: An assessment of the germination of African oil bean seeds as affected by crude oil pollution of soil was carried out in Asaba, Nigeria in 2008. Six (0.0, 1.4, 2.8, 5.3, 11.2 and 22.4% by weight per 1.6kg of weight of soil sample) crude oil concentrations in soil served as the treatments. A randomized complete block design was adopted with four replications.
Results: The results showed that no significant differences (P>0.05) existed between the Pentaclethra macrophylla seeds sown in the unpolluted (0.0%) and those planted in the 1.4% level of oil pollution as regards percentage germination, days to germination and rate of germination. Significant differences (P≤0.05) were however observed in the germination characteristics of P. macrophylla seeds sown in soils as the concentration of oil in soils increased.
Conclusion: The study has established that crude oil pollution of soil has a significant effect of reducing the viability of Pentaclethra macrophylla seeds. It is also demonstrated in the study that crude oil application to soil significantly delayed and reduced the rate of germination of Pentaclethra macrophylla seeds while the minimum (critical) level of crude oil pollution that Pentaclethra macrophylla seeds can tolerate with respect to germination is 1.4% wet weight.