effect of host plant on the virulence of entomopathogenic fungus beauveria bassiana against tetranychus urticae and predatory bug orius niger

as the host plants based on their physical and chemical characteristics can affect virulence of microbial control agents on the target pest and its natural enemies, therefore in the current study, the virulence of beauveria bassiana tv isolate at concentration 107 conidia/ml was evaluated against t. urticae female adults, on three different host plants; tomato, cucumber and strawberry. spray tower method with five replications was used in this research. in control, the spider mites were not treated by b. bassiana. afterward, the sensitivity of fifth instar nymphs and six-day olds adult females of predatory bug, o. niger was investigated to the fungus at concentration of 107 conidia/ml on these three host plants with five replications. the experiments were conducted in a completely randomized design. variance analysis revealed that the effect of this isolate was different statistically against t. urticae on three plants. mean comparisons using f-lsd demonstrated that the highest mortality of mites with 63% was observed on cucumber compared to tomato and strawberry which were 57% and 50%, respectively. based on the results, these three host plants did not affect the virulence of isolate tv on o. niger female adults and nymphs. our findings showed, isolate tv is highly toxic to spider mite population tested in laboratory. also, obtaining a good control result for a biological agent against a particular pest on a specific host plant, does not necessarily mean that the agent is effective on the same target pest but different host plant.