Mosquito Larvicidal Bacillus Strains From Ethiopia
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Date
1996-04
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Addis Ababa University
Abstract
Four strains of laIVicidal bacilli isolated from soil and dead mosquito lalvae in
Ethiopia and two intemational standard strains, Bacillus tituringiensis var.
israelensis; IPS-82 and Bacillus sphaericus, SPH-88, were investigated for their
lalvicidal potential using laIVae of the mosquito species, Culex: quinquefasciatus
and Anopheles arabiensis. Among the four media types selected for cultivation of
the strains, medium-2 and medium-3 were found suitable to enhance the toxicity
of the Ethiopian strains. Moreover, culture incubation temperature and aeration
rate were found to affect the laIVicidal potential of the Ethiopian strains. The
laIVicidal efficacy (LCso values) of the Ethiopian strains ranged from 0.0086 mgll
for Bacillus NA-82 on second instar laIVae of Cx. quinquefasciallls to 221.6 mgll
for Bacillus NA-6 on third instar laIVae of All. arabiensis. IPS-82 showed the
highest laIVicidal efficacy with LCso value of 0.0010 mgll against second
instar laIVae of All. arabiensis. Two of the Ethiopian strains and IPS-82 showed a
higher toxicity on larvae of All. arabiensis than on Cx. quinquefasciallls. All
Ethiopian strains have high degree of morphological and biochemical similarities
to the reference strain of B. tilllringiensis var. israelensis (IPS-82) and have been
taxonomically classified as strains of B. Ihuringiensis. Moreover, serological
characterization revealed that two of the Ethiopian strains, Bacillus NA-6 and
Bacillus NA-71 are identical to B. tJllIringiensis var. seoulensis. The other two
strains, Bacillus NA-IO and Bacillus NA-82 showed low level of titers to two of
the type antisera tested and thus are possibly new serotypes of B. IJllIringiensis.
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Biology