Evaluation of larvicidal potency of some entomopathogenic bacteria isolated from insect cadavars on Anopheles arabiensis larvae in Nigeria

The laboratory evaluation of larvicidal activities of some bacteria namely; Pseudomonas aeruginosa, Bacillus polymyxa and Bacillus subtilis was assessed against the second and fourth instar of Anopheles arabiensis collected from South West Nigeria. Concentrations ranging from 1.3 X10 7 cfu/mL to 6.5 X 10 7 cfu/mL were tested on the larvae for a period of 48 h. The disparity in the activities was monitored with Bacillus subtilis displaying the highest activity in both the second and fourth instar with LC50 of 0.865 and 2.361 mg/mL respectively. Pseudomonas aeruginosa showed LC50 of 1.931 and 4.205 mg/mL while the least activity was recorded in Bacillus polymyxa with LC50 of 5.776 and 7.403 mg/mL. There were significant differences in the LC50 value of the bacteria on tested instars. Values obtained from the fourth instar group were significantly different from those obtained from the second instar group in all the treatments. Finding from this study showed that B. Subtilis may be a potential biocontrol agent of Anopheles arabiensis, the main malaria vector in Nigeria.