Botanical larvicides have featured prominently as alternative to synthetic chemical
insecticides which are less degradable and toxic to non-target organisms. The larvicidal potentials of
the seed oils of
Pterocarpus santalinoides
and Tropical Manihot species (TMS 30572) were investigated
in the laboratory against larvae of
Aedes aegypti
. The seed oil of each plant was extracted using nhexane
and was graded into different concentrations; 30, 60, 90, 120 and 150ppm. The toxicity of each
of the concentrations was evaluated against 3
rd instar larvae of
A. aegypti and tadpoles (Buffo spp) as
non target aquatic fauna. Both oils were toxic to the larvae though at higher concentrations (120ppm
and 150ppm) after 24 hours of exposure. The oil of
P. santalinoides was more toxic to the larvae (LC
50
104.0ppm and LC
90 184.5ppm) than oil of TMS (LC
50 113.5 and LC
90 201.2) but the difference in the
lethal doses was not statistically significant (P>0.05). However, mortality was not recorded at any of
the graded concentrations in both oils against tadpoles. The results therefore suggest that the seed
oils of both plants could be incorporated as botanical insecticides against mosquito vectors with
high safety to non- target organisms.
