Abstract:
The molluscicidal activity of Coleus blumei Benth., Pittosporum resiniferum Hemsl. and
Sanseviera sp. Thunberg against Oncomelania hupensis quadrasi Moell. was
investigated using niclosamide as positive control. One hundred percent crude extract of
Coleus blumei Benth. was used against the snails. Snail activity was retarded on the first
six hours after which fluctuations in activity were observed. Snail mortality is six
percent. One percent crude extract and supernate were prepared from Pittosporum
resiniferum Hemsl. fruit extract. Pittosporum resiniferum Hemsl. crude extract showed a
fluctuating trend in snail activity. The supernate retarded snail activity for the first six
hours after which fluctuations in snail activity also occurred. Snail mortality for both
crude extract and supernate is two percent. One percent Sanseviera sp. Thunberg, on
both primary and secondary tests showed an initial retardation of snail activity on the first
six hours. Fluctuations in snail activity were observed until the end of the observation
period. Mortality is sixty percent and sixteen percent on the primary test and secondary
test, respectively. The difference may be accounted for a) the snail source and b) the
probable decrease in potency of Sanseviera sp. Thunberg extract through time.
Niclosamide at 10 ppm exhibited total retardation of snail activity in two hours.
Furthermore, ninety-eight percent mortality was observed. Niclosamide still remains to
be the molluscicide of choice.
