Synergistic Effect of Some Entomopathogenic Fungi and Synthetic Pesticides, Against Two Spotted Spider Mite, Tetranychus urticae Koch (Acari: Tetranychidae)

Abstract

Spider mites are emerging as major pests in many field crops including cotton in Pakistan. The present study was carried out to evaluate the effect of some strains of entomopathogenic fungi viz., Metarhizium anisopliae, Paecilomycis fumosoroseus (Pf) and Verticillium lecanii on two spotted spider mite, Tetranychus urticae Koch, a pest on cotton during summer 2010. Three concentrations i.e., 1x 10 6 , 1x 10 7 and 1x 10 8 conidia mL -1 of each fungal strain were used against eggs and adult females of mites. All tested fungal isolates were pathogenic to both the eggs and adult females. The mortality in adult females increased with increase in conidial concentration while the % hatching in eggs decreased with increase in conidial concentration. The most virulent isolate against adult females was Pf (n32) with lowest LC50 value (9.1 × 10 4 conidia/ml on 8 th day post treatment) and LT50 value (4.58 days at 1 × 10 8 conidia mL -1 ) followed by V17 isolate with LC50 value (1.7 × 10 6 conidia mL -1 ) and LT50 value (5.45 days at 1 × 10 8 conidia mL -1 ). Combined treatment of cotton with Pf (n32) and chlorfenapyr, an insecticide, proved best combination causing more than 90% mortality.The results indicated that P. fumosoroseus strains have potential as microbial control agent against T. urticae in Pakistan.