Virulence of four Beauveria bassiana (Balsamo) (Asc., Hypocreales) isolates on rose sawfly, Arge rosae under laboratory condition

Rose sawfly Arge rosae (Hym; Argidae) is the most serious pest of the flowers of Rosaceae family. In order to evaluate the potential of entomopathogenic fungi for controlling this pest, fourth instar larvae were maintained under controlled conditions and exposed to entomopathogenic fungi, Beauveria bassiana. The bioassay was carried out by immersion method with concentrations 2 × 104, 2 × 105, 2 × 106, 2 × 107, and 2 × 108 conidia/ml of Tween-80 solution (0.03%) in distilled water. Each concentration was replicated four times with ten insects in each replicate. The results showed relatively high efficacy of these isolates on this insect pest. In case of IRAN 403C isolate, values of LC50 and LT50 were obtained as 5.54 × 105 conidia/ml and 3.92 days at 2 × 108 conidia/ml, respectively. Results showed that IRAN 403C isolate caused the highest mortality in larvae in comparison with other isolates with a mean of 70% mortality using 107 conidia/ml.