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[Display omitted] • Chemical control of rice insect pests is prohibited in rice-shrimp rotation fields. • Two mycoinsecticides are tested for efficacies against rice leaf-rolling insect pests. • B. bassiana is more efficacious than M. anisopliae against the pests in the field. • Better control results from fungal spray after 5:00 pm than that before 10:00 am. Beauveria bassiana ZJU435 (Bb-ZJU435) and Metarhizium anisopliae CQ421 (Ma-CQ421) registered as mycoinsecticides in China were tested for control efficacies against the rice leaf-rolling pests Cnaphalocrocis medialis and Parnara guttata, which migrated to the tillering stage of rice crop in three rice-shrimp rotation paddy fields, where chemical control is prohibited. Either mycoinsecticide was sprayed twice at a recommended rate after 5:00 pm to avoid solar UV avoidance (UVavo) or before 10:00 am to increase solar UV exposure (UVexp). The first spray, although followed by two-week harsh weather, reduced significantly leaf roll densities (damages) in the fungal treatments compared to blank control. The UVavo and UVexp treatments resulted in control efficacies of 63 % and 35 % for Ma-CQ421 and 28 % and 16 % for Bb-ZJU435 on day 14. The second spray was followed by two weeks of weather favorable for fungal action. Consequently, Bb-ZJU435 and Ma-CQ421 showed significantly higher efficacies in their UVavo treatments (60 % and 55 % on day 21; 66 % and 64 % on day 28) than in corresponding UVexp treatments (47 % and 43 % on day 21; 53 % and 50 % on day 28). The UVavo versus UVexp efficacies after the second spray were corrected to ∼95 % versus ∼85 % for Bb-ZJU435, and 75–84 % versus 54–68 % for Ma-CQ421 by verifying whether the leaf rolls were empty (damage-transferred) or occupied by a living or mycosis-killed larva in all treatments. The corrected efficacies of Bb-ZJU435 were significantly higher than those of Ma-CQ421. Conclusively, either mycoinsecticide was more efficacious against the rice leaf rollers when applied in late afternoon to avoid solar UV damage. [ABSTRACT FROM AUTHOR]