Aedes aegypti is the primary vector of
dengue,
yellow fever and chikungunya in India and other South East Asian countries, and novel
insecticides for vector control are urgently needed. In the present investigation, efficacy of
potash alum, a traditionally known double
salt in Indian and Chinese medicine system, was tested against the larvae of
dengue vector, A. aegypti. LC(50,) LC(90) and LC(99) values were recorded for various instar larvae where I instar larvae were found to be the most susceptible and IV instar larvae as the least susceptible one. The LC(50) values of crude and standard
potash alum of various instar larvae ranged between 15.29 and 48.53 ppm and 20.50-65.10 ppm, respectively. Biochemical changes were also evidenced in IV instar A. aegypti larvae following a sublethal exposure for 24 h in the levels of various nutrient reserves and primary metabolites such as
sugar,
glycogen,
lipids and
proteins suggesting possible mode of action responsible for larval mortality.
Sugar and
glycogen concentrations were measured as 24.6 and 10.67 μg per five larvae in controls which were significantly (p<0.05) reduced by 32.11-93.98% and 39.26-94.47%, respectively, in larvae treated with crude
alum. In controls,
protein and
lipid content were recorded as 210.74 and 94.71 μg per five larvae which dropped up to 26.53% and 25.5%, respectively, in larvae following treatment with crude
alum. Moreover, drastic changes were also recorded for
DNA content with 25.39-44.17% decrease in crude
alum-treated larvae. It is evident from these results that
potash alum, a fairly cheaper and readily available ecofriendly compound could be recommended as a potential chemical larvicide against
dengue vector at mosquito breeding sites in the vicinity of human dwellings.