The efficacy of some local isolates of the fungus Beauveria bassiana (Bals.) Vuil. on The tomato leaf miner, Tuta absoluta (Meyrick) Larvae

Abstract

The tomato leaf miner, Tuta absoluta  is among the most destructive pests that attack tomato in many countries. In this study, the efficiency of three suspensions (2×10⁴, 2×10⁶ ,2×10⁸ spore/ml) of four different local isolates (b6, b7, b8, b10) of the entomopathogenic fungus Beauveria bassiana was investigated against  T. absoluta larvae 1^fr,2^nd, 3^rd and 4^th instar under laboratory condition for eight days to study the effect of these isolates  at that  different concentration  on larval mortality .  The results showed significant differences of mortality rate among the isolates themselves as well as between them and the control treatment. Corrected mortality rates at the highest concentration (2×10⁸ spore/ml) were (71.85، 60، 68.89، 58.89%) for b6 isolate  and (60.74، 49.63، 58.52، 58.15%) for b7 isolate, and (100، 100، 92.9، 89.63%) for b8 isolate and for b10 isolate were (100, 96.30, 96.67, 92.96%) on 1^fr,2^nd, 3^rd and 4^th instar larvae, respectively. The LT50 for four isolates at the same concentration was 4.9, 5.8, 4.7, 6.4 days for b6 isolate and 5.7, 7.5, 6.7, 6.2 days for b7 isolate and 3.2, 3.4, 3.8, 3.9 days for b8 isolate, and for b10 isolate was 3.4, 3.6, 3.7 and 3.7 days for 1^fr,2^nd, 3^rd and 4^th instar larvae, respectively. While the LC50 values  were ( 4 x 10⁴, 4 x 10⁶, 1 x 10⁶, 4 x 10⁶ spore/ml) for b6 isolate, (2 x 10⁶, 5 x 10⁸, 7 x 10⁵, 2 x 10⁷ spore/ml) for b7 isolate, (2 x 10⁴, 3 x 10⁴, 2 x 10³, 3 x 10³ spores/ml) for b8 isolate, (2 x 10⁴, 3 x 10³, 3 x 10³, 5 x 10⁴ spores/ml) for b10 isolate on 1^fr,2^nd, 3^rd and 4^th instar larvae, respectively.