Entomopathogenic fungi are promising microbial agents for agricultural pests, especially piercing-sucking insects. In this study, eight indigenous fungal isolates including four isolates of Metarhizium brunneum and four isolates of Beauveria bassiana were tested on Orosanga japonica Melichar (Hemiptera: Ricaniidae) in order to find an effective control agent that can be utilised for the development of oil-based fungal mycoinsecticides. In the screening test using 1 x 10(7) spores ml(-1) concentration, KTU-24 (B. bassiana) and KTU-51 (M. brunneum) had the highest lethal activity against nymphs and adults of the target pest. Also, at the highest concentration (10(9) spores ml(-1)), KTU-24 showed 92.33 and 94.88% mortality on nymphs and adults at the dose-response tests, respectively, and the KTU-51 isolate showed 100% mortality on both stages of O. japonica under laboratory conditions. With these results, KTU-24 and KTU-51 isolates were used to develop biopesticides. While the mass production of B. bassiana was carried out with liquid-state fermentation, solid-state fermentation was used for mass production of M. brunneum. Spores of both isolates were formulated in oil, and products were named as RICANICIDAL Bbas-TR61 and RICANICIDAL Met-TR61, respectively. Formulations caused over 97% mortality against nymphs and adults of O. japonica under field conditions and both formulations showed higher efficacy than commercial mycoinsecticides at 10(8) spores/ml concentration 20 days after treatment. The currents study shows that both mycoinsecticide formulations are highly promising for management of O. japonica.