Field evaluation of Aspergillus oryzae XJ-1 as a potential biological control agent against grasshoppers in arid grasslands of northwestern China

More than 100 grasshopper species occur in the Xinjiang Uygur Autonomous Region of China, several of which periodically cause severe damage to rangelands. Aspergillus oryzae XJ-1, a fungal pathogen originally isolated from a grasshopper in Xinjiang, has previously shown pathogenicity against several locust and grasshopper species in laboratory and cropland studies, but its efficacy in natural grasslands remained unknown. We evaluated its pathogenicity and field efficacy through infection assays, field-cage experiments, and field trials conducted in Xinjiang from 2024–2025. In field-cage experiments, cumulative mortality of adult Oedipoda miniata and Calliptamus barbarus reached 73.3 ± 8.8% and 76.7 ± 6.7%, respectively, 20 days after treatment. Field applications reduced grasshopper populations by up to 84.9% within 15 days. Mycelial growth of A. oryzae XJ-1 was observed on cadavers of seven grasshopper species collected from treated plots. These results demonstrate the pathogenicity of A. oryzae XJ-1 under field conditions and suggest that this indigenous fungal isolate has promising potential as a biological control agent against grasshoppers in the arid grasslands of northwestern China.