Spots on leaves are small and circular but tend to form elongated streaks. When pods are heavily spotted, the fungus penetrates the seed. Seed development may be hindered by this disease. Downy mildew has caused considerable damage to common vetch in the Pacific Northwest. The underside of infected leaves is covered with fine grayish fungal threads.
Infected leaves turn yellow and drop off prematurely.
Stem rot of vetch is caused by a fungus that is destructive during cool, wet weather. This disease sometimes causes considerable damage in the Pacific Northwest. Root-knot nematode can cause considerable damage in vetch. Nematodes are most active in warm weather, and damage may be reduced by moderately late planting. Resistant varieties may offer the best means of control of vetch diseases.