A simplest, rapid, reliable, and cost-effective staining method of the hypocotyls in the infected lupine plants was modified from Woodbury method for Native PAGE catalase to define the role of the fungal catalase produced by F. oxysporum on the reactive oxygen species (ROS) of Lupinus termis during infection. Fresh sections in hypocotyls of the infected plant and control ones were taken and stained directly on a glass slide. The visual detection of oxygen evolution from the xylem vessel, as a fungal catalase activity, gives a potential evidence for its role in embolism formation and wilt disease. White and blue color indicates the presence of catalase and H2O2 respectively. The catalase activity was significantly increased in the fungal growth medium than in the control plants. A model has built up to summarize the role of fungal catalase in the embolism formation, water current disconnection, and wilt disease.