Mosquitocidal Activity of cyt Positive Bacillus thuringiensis Isolated from Soil Samples

Bacillus thuringiensis (B.t.) produces parasporal inclusion bodies Cry and Cyt proteins. The present study focuses on determining the insecticidal activity of cyt positive B.t. strains against 3rd instar larvae of mosquito. Larval mortality was noted after 24 h and GCU B.t. 4 (400 ± 1.15) was found to be the most toxic against 3rd instar larvae of mosquitoes. Spores LC50 values of other isolates were 451 ± 0.90 (GCU B.t. 1), 511± 0.85 (GCU B.t. 2), 525 ±.013 (GCU B.t. 5), 582 ± 0.66 (GCU B.t. 3) and 850 ± 0.34 (GCU B.t. 6). GCU B.t.4, with LC50 value of 68 ± 0.46 µg/ml was the most toxic B.t. isolate while other B.t. strains GCU B.t. 1 (75 ± 0.95), GCU B.t. 2, (93 ± 0.88), GCU B.t. 5, (106 ± 1.32), GCU B.t. 3 (106 ± 0.95) and GCU B.t.6 (118 ± 1.55) showed LC 50 values in decreasing order, respectively. These bacterial isolates have a great potential to grow into a bioinsecticidal formulation for the control of mosquitoes.