Abstract

The laboratory evaluation of larvicidal activities of some bacteria namely; Pseudomonas aeruginosa, Bacillus polymyxa and and Bacillus subtilis was assessed against the second and fourth instar of Anopheles arabiensis collected from South West Nigeria. Concentrations ranging from 1.3 x 10⁷cfu/mL to 6.5 x 10⁷ cfu/mL were tested on the larvae for a period of 48 h.  The disparity in the activities was monitored with B. subtilis displaying the highest activity in both the second and fourth instar with LC₅₀ of 0.865 and 2.361 mg/mL respectively. P. aeruginosa showed LC₅₀ of 1.931 and 4.205 mg/mL while the least activity was recorded in B. polymyxa with LC₅₀ of 5.776 and 7.403 mg/mL. There were significant differences in the LC₅₀ value of the bacteria on the 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 show that B. subtilis may be a potential biocontrol agent of A. arabiensis, the main malaria vector in Nigeria.

Key words: Biocontrol, larvicidal activities, Anopheles mosquito larvae, malaria.