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.