Infection process and pathogenicity of Beauveria bassiana (Balsamo) Vuillemin against Tetranychus urticae Koch

The two-spotted spider mite, Tetranychus urticae is an important pest worldwide, the incidence of which led to reduce crop yields or poor marketability of the produce, both under field and protected cultivation. Insecticides usage for management lead to problems of resistance and residue and mycoinsecticides are the best alternative. Hence in this study, the infectivity of a native isolate of the entomopathogenic fungus, Beauveria bassiana MK918495 to T. urticae was revealed through scanning electron microscope and pathogenicity studies. SEM photographs taken at different hrs after infection showed the processes of infection, viz., adhesion, germination, penetration, colonization, extrusion and conidiogenesis on different body region of mite at 24 hrs, 48–72 hrs, 72–96 hrs, 96–120 hrs, 120 hrs and 120–144 hrs, respectively. The efficacy of the isolate was evaluated against T. urticae at different concentrations ranging from 4×10⁴ to 4×10⁹ spores mL⁻¹ and the result showed that the mortality ranged from 27.6 to 89.2% at 7 days after treatment. The LC₅₀and L_C90 of B. bassiana spore suspension were worked out to be 1.0×10⁶ and 2.1×10⁸ spores mL⁻¹, respectively.