: Efficacy of Iranian Isolate of Beauveria bassiana against Russian wheat aphid Diuraphis noxia (Mordvilko) (Homoptera:Aphididae) on the Laboratory conditions

In this study، the effects four Beauveria bassiana isolates، obtained from soil of Fashand، Atashgah & Ghare-agaj and one from a grass hopper Sphingonotus. sp on adults of adult Russian wheat aphid Diuraphis noxia was studied under laboratory conditions. After determination of the minimum & maximum concentrations، the adults Russian wheat aphid were treated with conidial concentrations of 1×103 to 1×10 6 spore/ml to calculate LC50 & LC90. DEBI002 proved to have the lowest LC50 (4 ×105 spore/ml) whilst DEBI010 showed the highest LC50 (2. 5×106 spore/ml). The lowest LT50 was obtained 2. 8 days for DEBI002 at 1×10 6 spore/ml. In a completely randomized block design، the mortalities caused by the isolates on 6th & 10th days was as follows: At 1×10 5 spore/ml، on 6th days DEBI002 (34. 95% ± 3. 64)، DEBI015 (37. 1% ± 6. 11) & DEBI001 (32. 35% ± 1. 3) were classified as level A & DEBI010 (18. 74% ± 1. 91) as level B. on 10th days، at 1×10 5 spore/ml DEBI002 (45. 1% ± 1. 23)، DEBI015 (39. 48% ± 7. 21) & DEBI001 (39. 43% ± 2. 65) were classified as level A & DEBI010 (16. 23% ± 3. 9) as level B (Duncans Muitple Range Test).