Variability of the potency of some selected entomopathogenic bacteria (Bacillus spp. and Serratia spp.) on termites, Macrotermes bellicosus (Isoptera: Termitidae) after exposure to magnetic fields
In this study, the effect of exposing entomopathogenic bacteria isolated from macerated termite cadavers to varying intensities of a magnetic field for different periods of time on their pathogenic potential was examined; pathogenicity tests were carried out for each of the bacterial species. Two of the bacteria, Bacillus subtilis (Ehrenberg) Cohn and Serratia marcescens Bizio, were able to induce morbid effects on termites and both were re-isolated from the resulting cadavers. Reinfection using different concentrations of both bacteria was carried out on termites to determine the minimum lethal concentration required for pathogenicity. Bacillus subtilis was able to degenerate the termites at concentration values of 108 colony-forming units (cfu)/ml and S. marcescens at 107 cfu/ml. Both bacteria were then exposed to magnetic fields of different intensities for different periods of time, after which they were used for reinfection of healthy termites. Postinfection study after the exposure of termites to magnetic field-treated bacterial cells revealed no reduction in the entomopathogenic potency of S. marcescens. As the extensive use of chemicals to control insect pests has been found to have detrimental effects on people and the environment, there is a pressing need to discover and develop new entomopathogens to control these insects biologically. Therefore, bacteria discovered in this study to have entomopathogenic potency against termites may be further studied and formulated into either powdery forms or suspensions to be applied to infested wood or wood products.
Key wordsentomopathogens electromagnetic fields Bacillus subtilis Serratia marcescens
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