عنوان مقاله [English]
Helicoverpa armigera is one of the most important tobacco pests in allover the world. TIn this research, the interaction effects of combined use of 5 superior Bt isolates and one superior NPV isolate that in previous research of authors, were isolated from different parts of the northern of iran, By combining two concentrations of Bt (2 × 107 – 1 × 107 spore/ml) and two concentrations of NPV (103 – 104 POB/ml) investigated on mortality of 2th larvae of H. armigera as a completely randomized factorial design with 3 replications under laboratory conditions. The results showed that Bt isolates (12, 73, 72, 50) with (2 × 107 spore/ml) concentration in combination with NPV (104 POB/ml) had the most lethal effect, So that on 7 and 14 days after treatment, they had 100% lethal effects. The lowest mortality related to Bt-58 with (1 × 107 spore/ml) in combination with NPV (103 POB/ml), which on fourteenth days after applying the treatment, it caused only 42/2% mortality. LC50 of superior isolate (Bt-72) was equal to 7 × 106 spore/ml and superior isolate (NPV-10) was equal to 8/1 × 104 POB/ml. The results revealed that 1 × 107 spore/ml concentration of Bt in combination with both two NPV concentrations and also Bt (2 × 107 spore/ml) in combination with 104 POB/ml showed Additive effects. Synergistic interaction effects were observed in combination of the highest concentration of Bt (2 × 107 spore/ml) and the lowest concentration of NPV (103 POB/ml).