Browsing by Author "Seyoum, Aklilu"

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    Mosquito Larvicidal Bacillus Strains From Ethiopia
    (Addis Ababa University, 1996-04) Seyoum, Aklilu; Abate Dawit (PhD); Gemetchu Teferi (PhD); Gebremichael, Teshome(PhD)
    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.