Beauveria bassiana no controle biológico de estágios imaturos de Stomoxys calcitrans

Abstract

Abstract: Stomoxys calcitrans (Linnaeus, 1758) population imbalance has caused significant economic losses in animal productivity. Currently concern about environmental safety has fostered the research and development for alternative control methods. The present study evaluated the entomopathogenic potential of Beauveria bassiana CG 138, CG 228 and ESALQ 986 isolates using three different in vitro methods to treat S. calcitrans eggs, larvae and pupae. S. calcitrans larvae exposed to CG 138 isolate and control group have been examined by scanning electron microscopy to verify the fungus adhesion and development on cuticle and natural openings. The in vitro antifungal activity was evaluated by diffusion test on media solidified using the larvae homogenate and surface mucus of control and treated groups. The bacterium present in the larvae homogenate and surface mucus was identified by PCR method. The antifungal activity of this bacterium was evaluated using the three B. bassiana isolates. The protein, enzymatic and chromatography profiles of these samples were evaluated by electrophoresis in a sodium dodecyl sulfate-polyacrylamide, zymography and high-performance liquid chromatography respectively. The results observed in the present study showed that the S. calcitrans immature stages are able to develop when are exposed to the three fungi isolates under experimental conditions. The three different fungi exposure methods used did not reduce the flies emergence of S. calcitrans adults. There was antifungal activity when the CG 138 isolate was exposed to the homogenate of larvae treated with this fungus. A reduced development of CG 138 on larvae cuticle was observed by scanning electron microscopy. There were differences between the chromatographic, protein and enzymatic profiles from control and treated groups, indicating antifungal reaction. The bacterium was identified as Stenotrophomonas maltophilia and presented antifungal activity against the three isolates. The results suggested the CG 138, 228, and ESALQ 986 isolates presented saprophytic effect since did not change significantly the development of S. calcitrans immature stages, and therefore, are not indicated to be used as stable fly biocontrol agent.