Laboratory Evaluation of Three Selected Isolates of Entomopathogenous Fungi Beauveria bassiana, Metarhizium anisopliae and Paecilomyces fumosoroseus against the Red Spider Mite Tetranychus urticae Koch Complex (Acari: Tetranychidae)

The susceptibility of various developmental stages of the red spider mite Tetranychus urticae Koch Complex to three selected isolates of entomopathogenous fungi Beauveria bassiana, Metarhizium anisopliae and Paecilomyces fumosoroseus was investigated under an ambient environment of 28 ± 2°C and 90 ± 10% RH. The fungal isolates exerted significant variable effects on the larvae, nymph and the adult mites 7 days after treatment. The nymphs were significantly less susceptible to all the three entomopathogenous fungi compared to the adult mites. Metarhizium anisopliae significantly inhibited hatching up to 45%. Computed median effective concentration (EC50) against the adult females showed the lowest value with P. fumosoroseus being 1.008 x 104 with 95% FL for 1540-4.697 x 10^4 conidia mL^-1 followed by M. anisopliae being 1.061 x 104 with 95% FL for 427.4-10.47 x 10^4 conidia mL^-1 and B. bassiana being 1.21 x 10^4 with 95% FL for 744.1-9.831 x 10^4 conidia mL^-1 . Time required for 50% cumulative mortality (LT50) of the adult females at comparable dosage of 1 x 10^8 conidia mL^-1 was 3.0 days for B. bassiana, 4.1 days for M. anisopliae and 2.4 days for P. fumosoroseus. Thus, P. fumosoroseus was the most infective isolate with the shortest time to mortality compared to M. anisopliae and B. bassiana.