Anthracnose (fungus – Glomerella cingulata): Leaves, flowers and shoots are at first marked with whitish spots. These spots spread extensively so that the parts attacked finally wilt and die. Seed pods shrivel and lose their color. Heavy infection results in much loss of leaves. The wilting works downward from the tips of the younger shoots, which become whitish and sometimes break. With a hand lens, many small salmon-colored pustules bearing great quantities of spores can be seen on the diseased parts. Gather and burn all infected plant parts after the flower season. Choose only seed pods which are plump and sound in appearance for planting. Seed for planting should be selected from disease-free pods. An occasional application of fungicide during the growing season helps minimize disease.
Powdery Mildew (fungus – Microsphera alni): Whitish, powdery growth on upper side of leaf surfaces. Leaves shrivel and drop off. Dust with sulfur or spray with recommended fungicide.
Downy Mildew (fungus – Peronospora trifoliorum): Under moist conditions, the leaves become covered with a grayish moldy growth. Thick-walled, brown resting spores develop within the moldy tissue. Since this is not a serious disease of this host in America, control measures have not been developed.
Leaf Spots (fungi – Colletotrichum pisi, Isariopsis griseola, Phyllosticta orobella, Mycosphaerella pinodes): Infection is not normally severe and spotted leaves can be picked off and destroyed as soon as they appear.
Stem and Root Rot: (See the section on Stem and Root Rot)
White Mold (fungus – Ramularia deusta f. spp. odorati): This mold, which may cover both sides of the leaves, may be mistaken for powdery mildew. Faint, dull-colored, irregular, elongated spots, which may be somewhat sunken, appear. The spots on the leaf margins, at first water-soaked in appearance, later have a reddish-brown discoloration. Tufts of spore-bearing hyphae develop from the stomatal openings between the epidermal cells. Spray with recommended fungicide as soon as white mold is noticed.
Fasciation (bacterium – Corynebacterium facians): Dense witches’ broom, distortions and fasciations develop at the base of the stem or from below the soil line. Since the pathogen is seed-borne, plant clean seed.