Evaluation of mosquito larvicidal activity of fruit extracts of Acacia auriculiformis against the Japanese encephalitis vector Culex vishnui.

The larvicidal potentiality of crude and ethyl acetate extracts of fruits of Acacia auriculiformis was investigated against all the larval instars of JE vector Culex vishnui. The crude extracts showed good results against all the larval instars with highest mortality at 0.09%. Highest mortality was found at 300 ppm of ethyl acetate extract. Lowest LC50 value was obtained at 72 h for third instar larvae. Non target organisms tested, showed no to very less mortality to ethyl acetate solvent extract. Presence of N-H stretching, a C=O stretching, C=C and C-N stretching vibrations of secondary amide or amine group were confirmed from IR analysis. GC-MS analysis revealed the presence of three compounds namely Ethane 2-chloro-1,1-dimethoxy, Acetic acid, 1-methyl ether ester and [4-[1-[3,5-Dimethyl-4[(trimethylsilyl)oxy)phenyl]-1,3-dimethylbutyl)-2,6dimethylphenoxy)(trimethyl) silane, responsible for mosquito larval death.

Larvivorous potentiality of Puntius tetrazona and Hyphessobrycon rosaceus against Culex vishnui subgroup in laboratory and field based bioassay.

OBJECTIVES: This study assessed the predatory potentiality of two unexplored fishes, Puntius tetrazona and Hyphessobrycon rosaceus on Culex vishnui subgroup larvae in order to utilize natural resources to diminish mosquito population. Larval feeding rate was evaluated in laboratory under varying prey density and volume of water. The experiment was extended to semi field condition. RESULTS: Puntius tetrazona and H. rosaceus consumed from 66 to 600 and from 87 to 718 Cx. vishnui larvae respectively in laboratory condition at 10 prey density levels (100-1000 larvae) at an increment of 100 larvae at 2 l water volume. In semi field condition, a 78% reduction in larval density was observed at day 30 post introduction of P. tetrazona, whereas 91% reduction was noted on day 21 for H. rosaceus and in the subsequent samples no mosquito larvae were found in ditches. Withdrawal of predators from the ditches resulted gradual increase in larval density. Laboratory and semi field bioassay of both the species indicated their potentiality as efficient mosquito larval predator though H. rosaceus exhibited better performance than P. tetrazona. It is recommended to utilize these natural resources to diminish mosquito population in the countries of their native range.