Erisiphe polygoni 1. White, powdery coating on leaves, stems and pods. Leaves become dwarfed, yellow and misshapen. Circular spots in field. Stunted, pale yellow-green wilting plants.
Leaves curl downward.
Stems thick and brittle. Xylem tissues yellow to orange and then darken. Same procedures as seed rot and damping off. Use varieties resistant to Race 1. Long rotations may be necessary, if widespread.