Omar Ali Mondal
Department of Zoology, University of Rajshahi, Rajshahi-6205, Bangladesh
Ataur Rahman Khan
Department of Zoology, University of Rajshahi, Rajshahi-6205, Bangladesh
Derris indica, Larvicidal activity, Culex quinquefasciatus, Larvae
Rajshahi University Campus
Pest Management
Aquatic animal
Preparation of plant materials for extraction: The fresh leaves, fruit-cover, rootbark, root-wood, seeds, stem-bark, and stem-wood of D. indica were collected from the Rajshahi University Campus. Leaves: after collection the leaves were spread out to dry without heaping the material together. It was done under the shade avoiding direct sunshine. Fruit-cover: fruits were picked and the covers were opened to remove the seeds for the collection of fruit-covers and spread out to dry under the shade. Root-bark: roots were collected and were shaken and brushed to remove soil without washing them with water. Root-bark was collected by striping from the stem, and cut and dried thoroughly in a well ventilated place. Root-wood: after removal of the root-bark the root-wood was cut into small pieces as thin as possible. Wood chips were dried thoroughly in a well-ventilated place. Seeds: after peeling out the fruit covers, seeds were cut into small pieces and spread out under shade to dry. Stem-bark: stem bark was collected by striping from the stem and cut into small pieces as thin as possible. After collection the bark was dry thoroughly in a well-ventilated place. Stem wood: after removal of the stem-bark the stem-wood was collected and cut into small pieces as thin as possible and dried. After drying under the shade, the plant materials were powdered in a grinder separately avoiding excessive heat during grinding. Chemical extraction of the collected materials: The organic solvent chloroform was used for the extraction of seven different parts of D. indica separately. The ground dried materials, viz. leaves, fruit-cover, root-bark, root-wood, seeds, stem-bark, and stem-wood were extracted with sufficient amount of chloroform (500 g × 1500 ml × 3 times) for each of the items. Separate extracts were collected by the cool method after 72 hours of plunging for each of the materials. The extracts, thus, obtained through filtration and evaporation of the solvent as residue were kept in a refrigerator after proper labeling. Preparation of doses with the crude extracts for the larvicidal activity test: The chloroform extracts of the plant materials were applied against Cx. quinquefasciatus larvae. For the fruit-cover, leaf and stem-bark two mg of each of the extracts was initially dissolved in 200 µl of pure dimethyl sulfoxide (DMSO) to make them hydrophilic before adding 19.98 ml of water to get a concentration of 200 ppm separately which were used as stock solution A. From the stock solution A, 10 ml was taken (that was with a concentration of 200 ppm) and diluted up to 20 ml with pond water to obtain a concentration of 100 ppm and this was used as stock solution B from which different other doses were made by the serial dilution method. Then a series of following concentrations was made from the stock solution A: 200, 100, 50, 25, 12.5 and 6.25 ppm. For root-bark, root-wood and stem-wood one mg of each of the extracts were dissolved in 100 µl of pure DMSO to make them hydrophilic before adding 19.98 ml of water to get a concentration of 100 ppm separately, which were used as stock solution A. From the stock solutions A, 10 ml was taken (that was with a concentration of 100 ppm) and diluted up to 20 ml with pond water to obtain a concentration of 50 ppm and this formed stock solution B from which different doses were made by the serial dilution method. Then a series of following concentrations were made from the stock solution A: 100, 50, 25, 12.5, 6.25 and 3.125 ppm. For the seed extract 0.5 mg was initially dissolved in 50 µl of pure DMSO for each before adding 19.98 ml of water to get a concentration of 50ppm which was used as the stock solution A. A series of following concentrations were made from the stock solution A for each of the samples: 50, 25, 12.5, 6.25, 3.125 and 1.5625 ppm. Application of doses: The second instar larvae of Cx. quinquefasciatus were collected from mass rearing beakers in the laboratory and different concentrations, viz. 200, 100, 50, 25, 12.50, 6.25, 3.125 and 1.5625 ppm were applied to the rearing medium in which the larvae were released. The crude extracts were measured by electronic balance and were taken in small vials. 100 µl of DMSO was used for 25 ml crude extracts for emulsification. Ten ml pond water was taken in 25 ml test tubes, the crude extracts as different doses were added to test tubes and 10 larvae were released to the dose treated water. Three replicates for each dose and a control were maintained. Statistical analysis: The mortality of Cx. quinquefasciatus larvae was corrected by the Abbott’s (1925) formula.
Bangladesh J. Zool. 39(2): 137-145, 2011
Journal