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Potential for Culex pipiens to develop resistance against Bacillus sphaericus toxins
B A Soliman1, M K Tewfick, G A Hafez
1Department of Biological Science, Faculty of Education, Suez Canal University, Suez, Egypt.
Journal of the Egyptian Society of Parasitology
|February 24, 2001
Summary
Field populations of Culex pipiens mosquitoes show consistent susceptibility to Bacillus sphaericus. However, laboratory selection pressure induced significant resistance in Cx. pipiens larvae to B. sphaericus within 20 generations.
Area of Science:
- Medical Entomology
- Microbial Pest Control
Background:
- Culex pipiens mosquitoes are significant disease vectors.
- Bacillus sphaericus is a biopesticide used for mosquito control.
- Understanding mosquito susceptibility and resistance to biopesticides is crucial for effective vector management.
Purpose of the Study:
- To assess the susceptibility of field populations of Culex pipiens to Bacillus sphaericus.
- To investigate the potential for resistance development in a laboratory colony of Cx. pipiens under selection pressure from B. sphaericus.
Main Methods:
- Collected 180 field populations of Culex pipiens from Giza and Qualyobia over one year.
- Exposed laboratory Cx. pipiens larvae to Bacillus sphaericus strain 2362 at LC80 for 20 successive generations.
- Monitored changes in susceptibility and resistance (LC50, LC90, RR) in selected and unselected colonies.
Main Results:
- Field populations exhibited no significant variation in LC50 and LC90 values, indicating consistent susceptibility.
- The laboratory colony developed resistance to B. sphaericus, with a resistance ratio (RR) of 1.69 at the 10th generation (F10).
- Resistance magnitude increased to 33-fold by the 20th generation (F20) in the selected colony, while the unselected colony remained susceptible.
Conclusions:
- Field populations of Culex pipiens remain susceptible to Bacillus sphaericus.
- Continuous exposure to Bacillus sphaericus can lead to the rapid development of significant resistance in Culex pipiens laboratory colonies.
- Monitoring and resistance management strategies are essential for the sustainable use of Bacillus sphaericus in mosquito control programs.
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