Wildfire in soybeans is a relatively uncommon bacterial disease caused by Pseudomonas syringae pv. tabaci.
Foliar lesions are light to dark brown and usually have wide, yellow halos. Lesion diameter can be ½ inch or more. When lesions expand or grow together, and the dead tissue falls away, leaves develop a tattered look. Severe infection may result in early defoliation. Lesions are often larger than other bacterial diseases.
Wildfire lesions on soybean leaf. Image: T. Faske.
Wet and warm temperatures (75-82 F) favor development. Crop residue, seed, and alternate hosts may host the bacteria. Inoculum is spread with splashing water and wind-driven rain.