Mosquito host range and field activity of Bacillus sphaericus isolate 2297 (serotype 25)

Area of Science:

• Medical and Health Sciences
• Environmental Science
• Entomology

Background:

• Bacillus sphaericus is a bacterium with insecticidal properties.
• Mosquito-borne diseases pose a significant global health threat.
• Effective and environmentally sound mosquito control methods are needed.

Purpose of the Study:

• To evaluate the efficacy of two Bacillus sphaericus isolates (2297 and 2362) against various mosquito species.
• To assess the field performance and residual activity of Bacillus sphaericus larvicides in different habitat conditions.

Main Methods:

• Laboratory bioassays were conducted against 8 mosquito species from 3 subfamilies.
• Field trials evaluated primary powders of Bacillus sphaericus isolates in natural and simulated habitats.
• Larvicidal activity and residual efficacy were assessed in relation to habitat characteristics (shade, water clarity, organic enrichment).

Main Results:

• Mosquito species in the genus Culex were most susceptible, while Aedes spp. and Toxorhynchites r. rutilus were least susceptible.
• Both Bacillus sphaericus isolates demonstrated similar larvicidal activity.
• Residual activity was longer in shaded, shallow, clear water habitats and reduced in organically enriched or unshaded conditions.
• Isolate 2297 provided effective control for over 5 weeks in shaded clear water and at least 1 week in organically enriched habitats at 0.25 kg/ha.

Conclusions:

• Bacillus sphaericus isolates show potential for controlling Culex mosquito populations.
• Habitat characteristics significantly influence the efficacy and residual activity of Bacillus sphaericus larvicides.
• Optimized application in suitable habitats can enhance the effectiveness of Bacillus sphaericus-based mosquito control programs.