Spike Wheat blast severity in the spikes caused by the agent Magnaporthe grisea (Pyricularia oryzae). Symptoms: It can infect all above-ground parts of the wheat plant, but head blast, resembling Fusarium head blight in appearance, is the most common symptom in the field. Infected spikes become bleached and produce small shriveled seed or none at all. Wheat blast severity MgrisSev Wheat blast severity acronym scale_of entity attribute method_of variable_of