Abstract:
Polar constituents of Kotschya uguenensis Verdc. (Fabaceae) do not exhibit acute toxicity but cause growth
disruption of Anopheles gambiae s.s. Gile (Diptera: Culicidae) larvae with eventual death. Time-course larvicidal
effects of powders of root and stem barks and their crude methanol extracts in form of emulsions were compared
in the laboratory and in artificial semi-field ponds. Kotschya uguenensis powders of root and stem barks and
emulsions of their crude methanol extracts were assayed against An. gambiae s.s according to protocols of WHO
1996 & 2005. All formulations were equally effective under laboratory conditions giving 100% larval mortality
within three days at a dose of 50 μg/ml of the extracts or concentrations of powders corresponding to the same
level of extractable material. Under semi-field conditions, suspensions of the powder materials appeared to
perform better than emulsions of methanol extracts. Time taken to give 80% mortality (LT80) of larvae and pupa
at 0.1% w/v was 6.06 days for powders of root bark and 5.60 days for powders of stem bark. The LT80 for the
root bark extract at 200 μg/ml was 8.28 days while that for the stem bark methanol extract was 12.47 days. No
residual effects of the test materials on the larvae or pupae were evident in semi-field ponds 14 days after the reintroduction
of the test materials. Our results suggest that, for the control of anophelines in the field, a weekly
application of appropriate amounts of powders of K. uguenensis may be effective.
