Larvicidal activity of micronized aqueous suspension of calcium hydroxide against Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae)

In the search of alternatives for the control of mosquitoes of medical importance, we evaluated the larvicidal activity of micronized suspensions of calcium hydroxide [Ca(OH)2] against Aedes aegypti and Culex quinquefasciatus. Tests conducted under laboratory conditions determined a LC50 = 0.027% (LC90 = 0.096%) for A. aegypti and a LC50 = 0.092% (LC90 = 0.2%) for C. quinquefasciatus, at 24 h post-treatment. Considering that the LC50 for the less susceptible species killed 100% of larvae for both species at 48 h post-treatment, we decided to use the diagnostic concentration of 0.1% which eliminated 100% of larvae at 48 h under a simulated field trial. There was a residual effect for up to 84 and 70 days for A. aegypti and C. quinquefasciatus, respectively. Evaluation of Ca(OH)2 on breeding sites showed a larvicidal activity of 100% for up to 56 days. When the micronized Ca(OH)2 was incorporated at concentrations from 0.02% (w/v), a superficial film was formed which killed 100% of the larvae of both species after 24 h of contact, and the activity remains until the film broke apart due to stirring. The fact that Ca(OH)2 is cheap and the people in rural areas of Mexico and other countries know the handling procedures for this compound led us to consider that 0.1% suspensions of Ca(OH)2 could be used for mosquito control in deposits of water placed in human premises both in urban and rural areas.