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Title: Pathogenicity of Different Isolates of Bacillus thuringiensis to the Larvae of the Red Flour Beetle Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)
Authors: Naiema E. Gorashi; Hamadttu; A. Elshafie; Hamid A. Hamid ; Dirar H. Dirar
Aff: Environment and Natural Resources Research Institute, National Centre for Research, Khartoum, Sudan
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Keywords: Tribolium castaneum; Pathogenicity; Bacillus thuringiensis; Mortality; Isolates; Microbial Control
Abstract:In this study, several samples were obtained from soils collected from different locations in Sudan and from stored products dust and dead insects, with the objective of isolating entomopathogenic Bacillus strains. Thirty nine strains were isolated and identified morphologically and biochemically and their pathogenicity to the red flour beetle Tribolium castaneum was evaluated. The larvae of red flour beetle were introduced to wheat bran treated with 500 ppm concentration from each isolate. The isolates differed significantly in their pathogenicity, where mortality percentages ranged from 12.5% to 85% compared to 7.5% in the untreated control larvae. Approximately 59% of the 39 Bt isolates were found pathogenic (mortality =50%) to the red flour beetle. The maximum reduction in the amount of food consumed by the treated larvae was 50%, compared to that consumed by the larvae in the untreated control. The least amount of food consumed (14%) was observed when larvae were fed upon food treated with isolate Sh-13. The untreated control larvae consumed 26% of the amount of food provided. Regression analysis revealed differences in the lethal times between different isolates. The LT50 values varied from 96.7 hours to 188 hours.