▎ 摘　　要

Plasmopara viticola, a causal agent of grapevine downy mildew, is a widely distributed pathogen, which can cause destructive disease in field-grown grapevines. Although fungicides are used to treat the disease, fungicide-resistant strains have been emerging. In this study, we developed graphene oxide (GO)-Fe3O4 nanocomposites, which could effectively repress the germination of sporangia and inhibit the development of downy mildew. 50 mu g mL(-1) GO-Fe3O4 showed excellent protective and fungicidal activities. 250 mu g mL(-1) GO-Fe3O4 on grapevine leaves in the field could significantly decrease the severity of downy mildew, suggesting its potent curative effect. Moreover, GO-Fe3O4 had no significant toxic effects on grapevine plants even at the concentration twice that of the highest dosage (1000 mu g mL(-1)) used in this study. Our work suggested that GO-Fe3O4 would offer an important opportunity to develop new approach for controlling plant diseases.