Mosquito larvicidal and pupicidal efficacy of Solanum xanthocarpum (Family: Solanaceae) leaf extract and bacterial insecticide, Bacillus thuringiensis, against Culex quinquefasciatus Say (Diptera: Culicidae)

The bio-efficacy of Solanum xanthocarpum leaf extract and bacterial insecticide, Bacillus thuringiensis, were assessed against the first to fourth instar larvae and pupae of Culex quinquefasciatus, under the laboratory conditions. The medicinal plants were collected from the outskirt Bharathiar University, Coimbatore, Tamil Nadu, India. The shade dried plant materials were extracted by employing the Soxhlet apparatus with ethanol (organic solvent) for 8 h and filtered. The extracts were concentrated at reduced temperature on a rotary evaporator and stored at a temperature of 4°C. Both S. xanthocarpum and B. thuringiensis show varied degree of larvicidal and pupicidal activity against various stages of C. quinquefasciatus. The LC(50) and LC(90) of S. xanthocarpum against the first to fourth instar larvae and pupae were 155.29, 198.32, 271.12, 377.44, and 448.41 ppm and 687.14, 913.10, 1,011.89, 1,058.85, and 1,141.65 ppm, respectively. On the other hand, the LC(50) values of B. thuringiensis against the first to fourth instar larvae and pupae were 133.88, 157.14, 179.44, 206.80, and 240.74 ppm; the LC(90) values were 321.04, 346.89, 388.86, 430.95, and 492.70 ppm, respectively. However, the combined treatment of S. xanthocarpum?+?B. thuringiensis (1:2) material shows highest larvicidal and pupicidal activity of the LC(50) values 126.81, 137.62, 169.14, 238.27, and 316.02 ppm and the LC(90) values 476.36, 613.49, 705.29, 887.85, and 1,041.73 ppm against C. quinquefasciatus in all the tested concentrations than the individuals and clearly established that there is a substantial amount of synergist act. Therefore, the present investigation clearly exhibit that both S. xanthocarpum and B. thuringiensis materials could serve as a potential of highest mortality rate against the mosquito larvae laboratory as well as the field conditions. Since C. quinquefasciatus is a ditch breeder vector mosquito, this is a user and eco-friendly biopesticide for the control of mosquito vector management program.     

Confidence limits for lognormal percentiles and for lognormal mean based on samples with multiple detection limits

The problem of assessing occupational exposure using the mean or an upper percentile of a lognormal distribution is addressed. Inferential methods for constructing an upper confidence limit for an upper percentile of a lognormal distribution and for finding confidence intervals for a lognormal mean based on samples with multiple detection limits are proposed. The proposed methods are based on the maximum likelihood estimates. They perform well with respect to coverage probabilities as well as power and are applicable to small sample sizes. The proposed approaches are also applicable for finding confidence limits for the percentiles of a gamma distribution. Computational details and a source for the computer programs are given. An advantage of the proposed approach is the ease of computation and implementation. Illustrative examples with real data sets and a simulated data set are given.     

Antimalarial activity of Carica papaya (Family: Caricaceae) leaf extract against Plasmodium falciparum

ObjectiveTo determine the antimalarial activity of the ethanol leaf extract of Carica papaya (C. papaya), blood stages of CQ-sensitive and CQ resistant strains against Plasmodium falciparum (P. falciparum) as target species.MethodsC. papaya leaf was collected in and around Kalveerampalyam village, Coimbatore, Tamil Nadu, India. C. papaya leaf was washed with tap water and shade dried at room temperature. An electrical blender powdered the dried plant materials (leaves). The powder 500g of the leaf was extracted with 1.5 L of organic solvents of ethanol for 8 h using a Soxhlet apparatus. The crude plant extracts were evaporated to dryness in rotary vacuum evaporator. One gram of the plant residue was dissolved in 100 mL of acetone (stock solution) and considered as 1% stock solution. From this stock solution, different concentrations were prepared ranging from 2%, 4%, 6%, 8% and 10%, respectively.ResultsThe highest larval mortality in the ethanol leaf extract of C. papaya against the 1st to 4th instars larvae and pupae values of LC₅₀= 3.65%, 4.28%, 5.41%, 6.70%, and 7.50%, respectively. The LC₉₀values of 9.61%, 11.75%, 13.53%, 16.36%, and 16.92%, respectively. Plant extracts showed moderate to good antiparasitic effects. These four concentrations (25, 50,100 and 150 μg/mL) of ethanol leaf extracts exhibited promising inhibitory activity against the CQ sensitive strain with (IC₅₀) values 40.75%, 36.54%, 25.30%, and 18.0% and in CQ resistant 50.23%, 32.50%, 21.45%, and 23.12% against P. falciparum.ConclusionsIn conclusion, the results indicate the effective plant extracts have the potential to be used as an ideal eco-friendly approaches for the control of vector mosquitoes.     

Adulticidal and repellent properties of Cassia tora Linn. (Family: Caesalpinaceae) against Culex quinquefasciatus, Aedes aegypti, and Anopheles stephensi

Mosquitoes have developed resistance to various synthetic insecticides, making its control increasingly difficult. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The adulticidal and repellent activities of crude hexane, chloroform, benzene, acetone, and methanol extracts of the leaf of Cassia tora were assayed for their toxicity against three important vector mosquitoes, viz., Culex quinquefasciatus, Aedes aegypti, and Anopheles stephensi. The adult mortality was observed after 24?h of exposure. All extracts showed moderate adulticidal effects; however, the highest adult mortality observed was found in methanol extract. The LC₅₀ and LC₉₀ values of C. tora leaf extracts against adulticidal activity of (hexane, chloroform benzene, acetone, and methanol) C. quinquefasciatus, A. aegypti, and A. stephensi were the following: C. quinquefasciatus LC₅₀ values were 338.81, 315.73, 296.13, 279.23, and 261.03?ppm and LC₉₀ values were 575.77, 539.31, 513.99, 497.06, and 476.03?ppm; A. aegypti LC₅₀ values were 329.82, 307.31, 287.15, 269.57, and 252.03?ppm and LC₉₀ values were 563.24, 528.33, 496.92, 477.61, and 448.05?ppm; and A. stephensi LC₅₀ values were 317.28, 300.30, 277.51, 263.35, and 251.43?ppm and LC₉₀ values were 538.22, 512.90, 483.78, 461.08, and 430.70?ppm, respectively. The results of the repellent activity of hexane, chloroform, benzene, acetone, and methanol extracts of C. tora plant at three different concentrations of 1.0, 2.5, and 5.0?mg/cm² were applied on skin of forearm in man and exposed against adult female mosquitoes. In this observation, this plant crude extracts gave protection against mosquito bites without any allergic reaction to the test person, and also, the repellent activity is dependent on the strength of the plant extracts. These results suggest that the leaf solvent plant extracts have the potential to be used as an ideal eco-friendly approach for the control of mosquitoes. This is the first report on mosquito adulticidal and repellent activities of the reported C. tora against mosquito vectors from Southern India.