EVALUATION OF ACARICIDAL ACTIVITY OF PURPUREOCILLIUM LILACINUM ISOLATED FROM EGYPTIAN SOIL AGAINST TETRANYCHUS URTICAE

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Abstract
The study is aimed to isolate and identify a potential entomopathogenic fungus from fields infested with spider mites and evaluate them as a bio-rationale agent against Tetranychus urticae Koch., which is an important agricultural pest that infests horticultural crops in both field and greenhouses. Macroscopic and microscopic characteristics showed that the obtained entomogenous isolate was Purpureocillium lilacinum(formerly, Paecilomyces lilacinus). P. Lilacinum demonstrated mortality rates on adult females of T. urticae of 71.19 and 77.97% with conidial concentrations of and 1.6 , respectively, 10 days after application. Median lethal concentration of P. lilacinum was 2.85 106 conidia/ml. Enzymatic activity of P. lilacinum was evaluated. In this context, chitinolytic activity of P. lilacinum was relatively weak, since the clear halo obtained was only 4.43 mm in diameter. The activity of chitinase enzyme insignificantly increased over the incubation period of 10 days. In contrast, proteolytic activity of P. lilacinum was high and showed a clear zone (25.8 mm) around the colony after 10 days. So, it is concluded that P. lilacinum has a potential biological control againstT. urticae. Finally, evaluation of the ethyl acetate extract of P. lilacinum showed acaricidal potency since it exhibited LC50 values of 10.49 mg/ml for eggs and 30.75 mg/ml for adults. So, it is concluded that P. lilacinum has a potential biological control againstT. urticae.

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