Laboratory evaluation of powders and extracts
Growth inhibitory effect of Kotschya uguenensis
podwers and extracts were carried out in the laboratory using
Anopheles gambiae s.s. larvae. 20 late 3rd or young 4th instar larvae
in 100 ml of distilled water were exposed to various concentrations
(10, 50 and 100 μg/ml for the extracts, and 0.01, 0.05 and 0.1 %
w/v of powdered suspensions; WHO, 1996; 2005). An equal
proportion of Tween 80 was added to the control set of emulsions.
For the experiment involving powdered plant materials, distilled
water was used as blank. The test was triplicated from separately
reared batches of larvae. Numbers of alive larvae and pupae were
recorded every 24 h and any reduction in larval and pupal density
calculated using Mulla’s formula (Mulla et al., 1971):
% reduction = 100-(C1T2/C2T1) x 100%
Whereby C1 = pre-treatment larval density in controls,
C2 = post-treatment larval and pupal density in controls
T1 = pre-treatment larval density in treatments
T2 = post-treatment larval and pupal density in treatments
During the experiment larvae were fed on Tetramin® fish
food at 1 mg per beaker per day (water temperature 26 ± 2 oC).
Results from laboratory investigations formed the basis of
selecting the levels of concentrations of the emulsions or powders
used at semi-field experiments.