Evaluation of cypermethrin insecticides on the growth of some selected soil bacteria isolated from Makurdi, Middle Belt, Nigeria

In the present investigation, a total of 30 soil samples were collected from five different sites in Makurdi metropolis to investigate the effect of cypermethrin on some soil bacteria. Physicochemical properties of the soil samples from various sites were determined using standard procedures. Some selected soil bacteria such as Escherichia coli, Klebsiella spp., Bacillus spp., Staphylococcus spp. and Proteus spp. were isolated by the use of serial dilution and pour plating method. The percentage prevalence of Isolates shows that a total of 10 bacteria were isolated with samples from high level accounting for 50% of the isolates, North bank 30% and Wurukum samples 20%. Klebsiella spp. accounted for 30% of the isolates, Escherichia coli 10%, Staphylococcus and Bacillus spp. accounted for 20%. The resistance pattern of the isolates at different concentration (1-3%) of cypermethrin showed that all the isolates could grow in the presence of cypermethrin at 1% except Bacillus spp. However at 2%, only Klebsiella spp. grew; Staphylococcus spp., Escherichia coli and Bacillus spp. were inhibited and therefore showed no growth. These findings revealed that cypermethrin had effects on the soil bacteria at higher concentration inhibiting their growth but tolerated at lower concentration. Therefore, indiscriminate use of insecticides should be avoided and more eco-friendly means of pest control should be employed to reduce the negative impact of synthetic pesticides on beneficial soil organisms.