Anthracnose causes whitish spots on leaves and flower shoots. The infected parts shrivel up and the seed pods shrivel and lose color. Wilting progresses down infected shoots which may break off. Old plants are not easily killed. Infected plants are destroyed after flowering. No chemical control is listed.
Black rot attacks the plant crown within a few inches of the ground. The roots are destroyed and the ends are stubby and black. Infected plants are dwarfed, pale yellow and sickly. The stems are easily removed from crowns. The disease is worse in heavy cold soils. Avoid replanting where the disease is a problem. No chemical control is listed.
Downy mildew may cover the leaves with a gray mold during moist weather. No chemical control is listed.
A number of leaf spots attack sweet pea causing spotting of various types. These are usually not serious and spotted leaves may be removed. No chemical control is listed.
Fasciation causes masses of short, thick, aborted stems, with misshapen leaves, to form at the base of the plant. The upper parts of the stem appear normal but the plant is dwarfed. No controls have been developed.
The pea mosaic virus can infect seedlings three or four weeks old. The leaves are curled, mottled, and yellowed and the plants are dwarfed. The few flowers that form will have color breaks. Control the insects which carry the virus.
The spotted wilt virus causes mottled leaves and purplish spots on stems and leaves. The blossoms have discolored or bleached spots. Destroy infected plants and control the insects which carry the virus.
Bud drop is caused by poor culture and is made worse by low phosphorous and potassium, high nitrogen, and inadequate light.
Powdery mildew covers the plant with a white, powdery growth. Sprays of triforine of benomyl will control the problem.