PRELIMINARY EVALUATION OF BACILLUS THURINGIENSIS SEROTYPE 8.14 AND BACILLUS SPHAERICUS STRAIN 1593 FOR TOXICITY AGAINST MOSQUITO LARVAE IN THAILAND*

SOMSAK PANTUWATANA and AMPORN YOUNGVANITSED

ABSTRACT: The larvicidal activity of Bacillus thuringiensis serotype H-14 and Bacillus sphaericus strain 1593 against several species of laboratory-reared and field-collected mosquito larvae was studied.

The larvicidal activity of B. thuringiensis (H-14) for several species of mosquito larvae showed 2nd instar larvae of Aedes aegypti (Linnaeus) to be the most sensitive with 100% mortality in 20-40 minutes at high doses (10 -100 mg/liter). The 2nd instar larvae of Culex quinquefascilltus (Say), Ae. albopictus (Skuse) and a mixed population of C. mimulus (Edwards) and C. vishnui (Theobald) demonstrated onlymoderate sensitivity. The 3rd instar larvae of Anopheles dirus (Peyton & Harrison), 2nd and 3rd instar larvae of An. vagus(Donitz), 3rd instar larvae of An. macullitus (Theobald) and Annigeres subalbatus (Coquillett), and 2nd instar larvae of C. tritaeniorhynchus (Oiles) showed relatively low sensitivity. The 3rd instar larvae of Toxorhynchites splendens. (Wiedemann), and the 4th instar larvae of Mansonia uniformis (Theobald) and M. Indiana (Edwards) were not susceptible.

The larvicidal activity of B. sphaerkus (1593) against several species of mosquito larvae showed C. quinquefascilltus to be the most sensitive with 100% mortality in 24 hours (LC₅₀ in 2 days, 3.55 x 10³ spores/ml). The 2nd instar larvae of An. vagus, C. tritaeniorhynchus and a mixed popullltion of C. mimulus and C. vishnui. demonstrated intermediate sensitivity. The 2nd instar larvae of Ae. aegypti and Ae. albopictus, the 3rd and 4th instar larvae of An. dirus, An. minimus (Theobald). An. philippinensis (Ludlow), An. macullitus and 4th instar larvae of An. nivipes (theobald) demonstrated less sensitivity (LC₅₀ in 2 days, 0.2-1.5 x 10⁶ spores/ml). The 4th instar larvae of A. aubalbatus, M. uniformis and M. indiana were not susceptible.

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Department of Microbiology. Faculty of Science Mahidol University, Rama VI Road Bangkok 10400, Thailand

Received 24 February 1984