Larvicidal Effects of Metabolites Extracted from Nocardia and Streptomyces Species against the Forth Larval Stage of Anopheles stephensi (Diptera: Culicidae).

Background: Larvicidal agents can be produced using microbial resources, which are environmentally friendly, biodegradable, and economical. The study's goal was to evaluate the larvicidal activity of metabolites isolated from Nocardia (N. fluminea, N. soli and N. pseudobrasiliensis) and Streptomyces (S. alboflavus) bacterial species against Anopheles stephensi.

Methods: Four metabolites isolated from Nocardia and Streptomyces strains were exanimated for larvicidal activity. The experiments were performed for 24, 48, and 72 hours. 300, 350, 400, 450, 500, 550, and 600 μl of Actinobacteria metabolites were added to 100 cc of dechlorinated water. Fourth-stage larvae were placed in dechlorinated water as a control. LC₅₀ and LC₉₀ were calculated using toxicity data and analyzed.

Results: All metabolites had a statistically significant influence on mosquito larvae (P< 0.05). At 24, 48, and 72 hours, the LC₅₀ for N2 (N. fluminea) was 417, 386, and 370 ppm, respectively, and the LC₉₀ was 650, 595, and 561 ppm. Moreover, LC₅₀ for N4 (N. soli) was 389, 376, and 347 and LC₉₀ were 591, 565, and 533 and LC₅₀ for N5 (N. pseudobrasiliensis) was 390, 357, and 341 ppm and LC₉₀ were 589, 532 ppm. In addition, LC₅₀ for S921 (S. alboflavus) was 484, 416, and 382 ppm, and LC₉₀ was 701, 612, and 574 ppm.

Conclusion: The four bacterial metabolites tested in our study were found to have a notable effect on the mortality rate of Anopheles stephensi larvae, indicating their potential as natural larvicides. This is an effective technique for controlling Anopheles stephensi that has no detrimental environmental impact.