Effect of the entomopathogenic fungus Beauveria bassiana (Balsamo) on eggs and eclosing larvae of the tick Argas (Persicargas) persicus (Oken).

The present study was carried out to investigate the pathogenicity of the fungus Beauveria bassiana when diluted in triton X100 at concentrations of 10, 10, 10, 10, and 10 conidia/ml and sprayed on the eggs of the tick Argas persicus. For each concentration, three replicates were made (each included about 10-16 eggs). Scanning electron microscopy was used to examine the surface morphology of the eggs and their eclosing larvae after treatment with a selected concentration of 10 conidia/ml B. bassiana. Biological studies revealed that all treated eggs demonstrated a delay in the hatching period (a highly significant increase) and a marked decrease in the hatching percentage, which increased as fungal concentrations increased, reaching 30 days (p < 0.001) and 2.9%, respectively, using 10 conidia/ml. Total inhibition of both parameters was observed at higher concentrations (10 and 10 conidia/ml). Scanning electron microscopy of the eggs after using a concentration of 10 conidia/ml, revealed signs of fungal adhesion 2 days after treatment, whereas germination occurred after 7 days. Excessive conidiogenesis and sporulation on the egg surface were observed after 15 days of treatment. All eclosing larvae appeared paralyzed 1-4 days after hatching with many conidia covering their whole bodies. The findings suggest that the fungus affected tick larvae are either directly infected in the eggs or indirectly during eclosion.