Poplar trees suffer from a serious fungal disease caused by Cytospora chrysosperma that devastates plantations. Scientists discovered that three genes controlling enzyme complexes called NADPH oxidases are critical for the fungus to cause disease. When these genes are removed, the fungus cannot produce enough of a toxic acid it uses to attack trees, and the fungus cells become stressed and damaged. These findings suggest new ways to control the disease by targeting these enzyme complexes.