Mosquitoes are major vectors, in transmitting many diseases like malaria, filariasis, Japanese encephalitis and dengue fever etc, which are greatly, affecting human beings worldwide. Malaria is a major global health problem. There are estimated 247 million malaria cases with almost half of the global population at risk and nearly a million deaths each year. Several Anopheles species are responsible for transmission of malaria .i.e. Anopheles stephensi, An. Subpictus.
Control of mosquitoes primarily depends on chemical insecticides includes organochlorine, organophosphates, synthetic pyrethroids, IGRs etc, but all these chemicals have developed a feedback of environment ill-effect, have negative impact on non-targeted biota and most mosquitoes species have become physiologically resistant to these insecticides. These problems have highlighted the need for the development of new strategies for mosquito control. Botanical insecticides are naturally occurring products that are derived from plants. The use of plant extracts for insect control has several appealing features, as these are generally more biodegradable, less hazardous, and rich storehouse of chemicals of diverse biological activity.
The current study were carried out to evaluate the activity of methanol extract of leaves of C.fistula, and ripened fruits of P. nigrum against Anopheles mosquito. Among both of these plants the methanolic extracts of Piper nigrum (black pepper) were exhibited remarkable adulticidal and larvicidal potentials. The percentage mortalities were increased by gradual increase in extracts concentrations. Larvae were more susceptible to
these methanolic pepper extracts than adults. Larvae were showed mortalities even at very low concentrations. The LC50 values obtained by using probit analysis were 25.05 ppm and 12.05 ppm after 24 hrs and 48 hrs respectively, whereas LC90 were 78.63 ppm and 53.06 ppm respectively for aulticidal bioassays. Larvicidal assays were also showed good results having LC50 values as 3.87 ppm and 2.07 ppm after 24 hrs and 48 hrs respectively, whereas LC90 were 10.63 ppm and 6.56 ppm respectively.
Cassia fistula (golden shower) leaf extracts were also showed promising mosquitocidal efficacy against Anopheles stephensi. LC50 values obtained by using probit analysis were 35.13 ppm and 16.18 ppm after 24 hrs and 48 hrs respectively, whereas LC90 were 94.57 ppm and 76.43 ppm respectively for aulticidal bioassays. Larvicidal assays were also showed good results having LC50 values as 44.99 ppm and 24.40 ppm after 24 hrs and 48 hrs respectively, whereas LC90 were 106.12 ppm and 76.30 ppm respectively.
It is concluded that methanolic extracts of these plants Cassia fistula and Piper nigrum have high potential of adulticidal & larvicidal activities. So the extracts of these plants can be used as an alternatives to the conventional insecticides for long lasting mosquito problems as these are less hazardous and ecologically feasible. However, a lot of work on biochemistry as well as insectidal activity and on other aspects has to be done.