After blooming, purple blotches may appear on the leaves which in wet weather are covered with an olive-grey mold. Destruction of old plant parts in the fall is usually sufficient for control. Symptoms include spots of varied color and size which develop on the leaves. Control can be achieved by removal of plant debris in the fall. Chemical control is usually not necessary.
Plants are small and weak and produce no flowers.
Roots are short and stubby, and fine roots show galls about one-eighth inch in diameter. When sliced, these reveal brown areas containing many nematodes, small round worms that are also called eelworms. Planting heat-treated roots in a new location prevents reinfestation. Since many other species of plants may become infested with these nematodes, care should be taken to plant only nematode-free planting material. Buds remain small and turn black but no gray mold appears on them.