Sweet potato whitefly, Bemisia tabaci biotype Q has been recognized as one of the most destructive insect pests worldwide because of increased resistance to some insecticide groups. To develop an alternative control agent, the effects of different culture conditions such as fermentation methods, culture temperatures, initial inoculum concentrations, substrates and medium supplements on the conidial production of the isolate Isaria javanica Pf04 were assessed. The results demonstrated that conidia of the isolate could be economically produced by single-phase solid state fermentation on barley substrate at 25 °C with 10⁸ conidia/g of initial substrate concentrations. Using optimal conditions, the maximum conidial production obtained was 3.5 × 10⁹ conidia/g dry substrate after 15 d of cultivation. The conidia, which were produced on barley alone and barley with 5% additives of silkworm powder and moth larvae, were virulent against second instar nymphs of whitefly, providing ≥90% mortality.