EFFICACY OF THREE ENTOMOPATHOGENIC FUNGI AGAINST Tetranychus urticae (KOCH) UNDER LABORATORY AND FIELD CONDITIONS

Abstract

The two-spotted spider mite, Tetranychus urticae Koch, is now known as one of the most serious cosmopolitan mite pests of various crops throughout the world. The present study was carried out to evaluate the virulence of three commercial entomopathogenic fungi (EPFs) viz., Metarhizium anisopliae, Beauveria bassiana and Verticillium lecanii against T. urticae females in the laboratory and field conditions, Three concentrations used in this assay were 2 × 106, 2 × 107 and 2 × 108 conidia ml-1 in the laboratory condition and only the highest concentration was used in the field condition. The controls were treated with water. The lethal effects of fungus were assessed as percentages of daily mite mortalities compared to the control. The mite mortality rates increased with increasing conidial concentrations and days following treatment. The results showed that M. anisopliae caused the highest mortality of T. urticae varied from 33.33 to 95.00%, with LC50 value of 2.5 × 105 conidia ml-1 and LC90 value of 6.5 × 107 conidia ml-1 during 7 days, respectively at 65 ± 10% RH and 25 ± 2˚C in the laboratory. The V. lecanii caused 30.0 to 81.67% mortality and its LC50 values estimated of 9.3 × 105 conidia ml-1 while B. bassiana was potentially less virulent than others causing 21.67 to 76.67% mortality rate to T. urticae with LC50 of 2.1 × 106 conidia ml-1. In field condition against T. urticae, a concentration of 2 × 108 conidia ml-1 achieved significant efficiency. The relative control effects were 88.01, 76.85 and 81.65 % respectively, in M. anisopliae, B. bassiana and V. lecanii after 10 days of treatment. The results of this present experiment recommend that all selected EPF of this study are potentially virulent against T. urticae and can be used as natural and ecofriendly safe fungal microbial agents in the IPM program in combating the mite pests.