Physiological and molecular characterization of Metarhizium isolates and their acaricidal activity against Tetranychus urticae Koch (Trombidiformes: Tetranychidae)

Abstract

Background: The two-spotted spider mite, Tetranychus urticae Koch (Trombidiformes: Tetranychidae), is one of the most damaging mites in agriculture. Due to the concern for the intensive use of synthetic acaricides, entomopathogenic fungi represents a feasible alternative to T. urticae management. In the present study, 7 isolates of Metarhizium were characterized physiological and molecularly (based on the ITS1-5.8s-ITS2 rDNA) and evaluated for their acaricidal activity [mortality, mean and 90 lethal concentration (LC50: LC90) and mean and 90 lethal time (LT50: LT90)] against T. urticae under laboratory conditions. Results: Sequencing of the ITS1-5.8s-ITS2 rDNA region indicated that the 7 isolates belong to M. anisopliae. The isolates Ma114 (3.7 ± 0.006 mm day−1), Ma109 (3.5 ± 0.009 mm day−1) and Ma106 (3.5 ± 0.006 mm day−1) had the highest radial growth rate and Ma114 (92.2 ± 0.86%) and Ma108 (94.4 ± 1.07%) had the highest germination percentage. All isolates were pathogenic to T. urticae, causing mortality that ranged from 45.3 to 85.3%. The LC50 and LC90 were 1.2 and 2.8, 1.1 and 2.5, and 1.2 and 2.8 × 108 conidia mL−1 for isolates Ma110, Ma109 and Ma106, respectively, while the LT50 and LT90 were 7.7 and 16.5, and 7.2 and 16.1 days for isolates M110 and Ma109, respectively. Conclusion: The isolates Ma110 and Ma109 of M. anisopliae were moderately pathogenic and virulent against T. urticae.