Pod and stem blight kills the plants in the later stages of development. It can be identified by the numerous, small, black fruiting bodies (pycnidia) that appear on the stems and pods of infected plants. On the pods, the pycnidia are scattered; on the stems they usually are arranged in rows. The disease occurs over most of the United States. High humidity and rain favor the production and spread of the spores from the pycnidia. Wet seasons are likely to show more damage from pod and stem blight than dry ones. The disease is seed-borne. The fungus can also overwinter on diseased stems in the field. Sanitation, the use of disease-free seed, and crop rotation are recommended as control measures.

Stem canker and pod and stem blight were considered one disease for many years. A. W. Welch and J. C. Gilman at the Iowa Agricultural Experiment Station discovered in 1947 that two separate diseases were involved. They found that pod and stem blight attacks older plants nearing maturity. Stem canker kills plants earlier in the season. Stem canker appears to be more common in the Midwest, especially in Illinois, Indiana, and Iowa, than in other regions. It usually appears after mid-July. Dead plants, with the dried leaves still attached, may be the first indication of its presence. A brown, slightly sunken type of lesion girdles the stem, usually at the base of a branch or leaf petiole. The stem canker fungus does not produce pycnidia on the infected plant, but sexual fruiting bodies (perithecia) develop on dead stems in the field during the winter. The spores (ascospores) produced in them serve to spread the disease during the following season. Stem canker, like pod and stem blight, is seed-borne. Since diseased stubble in the field is a source of infection in both diseases, the same control measures are recommended as for pod and stemblight. We have no variety that is resistant to stem canker. Hawkeye seems to be very susceptible.

Anthracnose of soybeans is caused by two species of fungi. Each produces similar lesions on the petioles, stems, and pods of plants nearing maturity. The diseased areas have a dark, stubble-bearded appearance because of the dark spines (setae) that emerge from the numerous black, fungus fruiting bodies (acervuli) that develop. Glomerella glycines was first reported as the causal agent of the disease in the United States. More recently Colletotrichum truncatum, which causes stem anthracnose of lima bean, has been proved capable of attacking soybeans. The latter is probably the fungus most commonly associated with soybean anthracnose. When soybean seeds infected with either of these fungi are planted, many of the germinating seeds are killed in the ground. The seedlings from such seed that emerge from the soil often have brown, sunken cankers on the cotyledons. The fungus may grow from them into the young stem. Those preemergence and post-emergence seedling losses are probably more serious phases of soybean anthracnose than are the more evident symptoms on older plants. Seed treatment prevents some of the loss of seedlings, and thus improves the stand obtained from anthracnose-infected seed. It does not eliminate the disease, however, because both fungi can over-winter also in diseased stems left in the field. Fall plowing and rotation should be practiced to avoid outbreaks of the disease that may arise from over-wintered, diseased stems.

The first report of the frogeye disease of soybeans in the United States was from North Carolina in 1926. It is primarily a foliage disease and is characterized by an "eyespot" composed of a gray or tan center and a narrow, reddish-brown border. There is no chlorotic tissue around the spots. The reddish-brown color merges abruptly with the green of the normal leaf. Heavily spotted leaves usually fall prematurely, thus causing a loss to the hay and seed crops. Stem infections are less numerous and somewhat less conspicuous than those on the leaves. They appear in the field in large numbers only in late fall when the plants are maturing seed. Stem lesions are elongated and have some shade of red when young. They become brown, then smoke gray, or almost black with age. Pod infections also occur late in the season. The fungus frequently grows through the pod wall and infects the seed. The causal fungus overwinters on diseased leaves and stems and apparently is introduced into new fields and communities through the planting of infected seed. Seed treatment has failed to give satisfactory control of the disease in field tests. Crop rotation should aid in holding it in check. When frogeye is abundant in a field soybeans should not be planted on the land the following year. The disease has been increasing in prevalence in some areas. Experimental tests of susceptibility of varieties and strains have been conducted at the Indiana Agricultural Experiment Station.

Target spot affects primarily the soybean leaves. The fungus also causes spotting of the petioles, stems, pods, and seeds. On the leaves, the spots are reddish brown, circular or irregular in shape. They vary from pin-point size when immature to one-half inch or more in diameter. The larger spots are sometimes distinctly zonate, and the common name target spot was suggested by such zonation. The spots of dead tissue are frequently surrounded by a dull-green or yellow-green halo, thus resembling wildfire. They may be told from the latter by their reddish-brown color and by the zonation, if any. Narrow, elongated spots are some times observed along the veins on the upper leaf surface. On petioles and stems, the spots are dark brown and vary from mere specks to elongated, spindle-shaped lesions. Pod spots are generally circular, about one-sixteenth inch in diameter, with slightly de-pressed purple-black centers and brown margins. The fungus penetrates the pod wall in some cases and causes a small blackish-brown spot on the seed.

The disease was first reported in the United States in 1945. It quickly became prevalent on soybeans grown in the alluvial soil area near the Mississippi River in Louisiana, Mississippi, and Arkansas. It is known to occur also on the Coastal Plain in North Carolina, South Carolina, Georgia, Florida, Alabama, and Mississippi and in the hill section of Mississippi. It possesses the potentiality of becoming a serious disease of soybeans in the southern producing areas. It had not been reported in the Corn Belt States in 1953. Ogden, the variety grown most commonly in the South, has moderate resistance. Soybean breeders and pathologists are on the alert to prevent the release of new soybean varieties more susceptible to this disease than Ogden. The fungus attacks cowpeas as well as soybeans, and growing those two crops close together or in sequence probably should be avoided. Rotation and plowing under of crop refuse in the fall should be of aid in controlling target spot.

A spotting of soybean leaves caused by one or more species of Phyllosticta has been known to occur in the United States since 1927. In some years the disease has caused appreciable premature defoliation in localized areas, such as the Eastern Shore of Maryland and Southeast Missouri. The leaf spots are round to oval, light or dark brown in color, and approximately one-quarter inch in diameter. Spots near the margin of the leaf blade frequently coalesce to give the leaf margin a fired appearance. The small, black, fruiting dots of the fungus are found abundantly on the leaf spots. Severely attacked leaves fall from the plants prematurely. The fungus also causes lesions on the petioles and stems, which add to the total injury. Lesions on the soybean pods have been reported from Germany and were observed in the United States for the first time in 1951. An ascospore-producing stage of the causal fungus has been reported from the Orient but has not been observed in the United States. Plowing under the crop refuse in the fall should aid in controlling the disease by destroying much of the overwintering inoculum.

Downy mildew of soybeans is characterized in its early stages by indefinite yellowish-green areas on the upper surface of the leaves. In severe outbreaks, entire leaflets are thus discolored. As the disease progresses, those areas become grayish brown or dark brown and have yellowish-green margins. Severely infected leaves fall prematurely. A grayish and moldlike growth develops on the under surface of the lesions. The spores produced on the growth spread the disease from plant to plant. Besides these externally borne summer spores, the thick-walled resting spores develop within the leaf tissues. They overwinter in the fallen leaves and probably provide inoculum for infecting the next season's crop. The causal fungus also grows within the pods and covers part of the seeds with a white crust composed largely of the thick-walled resting spores. When such seeds are planted, a small percentage of the seedlings have the fungus growing within them. The first leaves to unfold on such seedlings usually are covered with mildew growth and thus provide centers of infection in the new season's crop. Downy mildew occurs throughout the soybean-growing areas of the United States. In some years it is one of the most prevalent soybean diseases. Severe epidemics have not been observed. The loss appears to be restricted to more or less premature defoliation, depending on seasonal conditions. The existence of races of the downy mildew fungus was proved by work conducted at the Wisconsin Agricultural Experiment Station. Differences in susceptibility have been observed in soybean strains and varieties. Should the disease become more severe, breeding resistant varieties would therefore appear to be possible.