Not known to transmit any human or animal pathogens.

No known vector

Infected young soybeans develop circular, dark red to brown lesions on their leaves along the veins. These can also occur on stems, petioles, and pods (Akem et al., 1992). Blotching and pycnidia occur on older lesions, with pycnidia (fruiting body containing spores) resembling ground black pepper in lesions on the upper leaf surface. Additionally, small (0.1-0.4 mm), dark brown to black sclerotia (hardened, compact mass of mycelia that can survive long-term) may be produced, typically on the lower leaf surface (Hartman, 2011). Most blotches have ash-gray centers with dark margins, and some are surrounded by yellow halos. Blotches are irregular and are 1/4 - 3/8 inches in diameter (Akem et al., 1992). Disease severity will be greater on leaves lower in the plant canopy (Hartman and Sinclair, 1996) and these should be targeted for visual survey.

See the CAPS datasheet for additional images of symptoms. 

Symptoms occur on soybeans at all stages of growth (Datnoff et al., 1986). However, at the early stage of infection, the symptoms are poorly developed, mostly confined to leaves, and could create confusion with the symptoms caused by other pathogens, such as Alternaria leaf spot. Clear diagnostic symptoms/signs are usually not seen until after flowering. Hence, surveys should begin at the beginning of flowering (R1) and continue through reproductive growth stages (Hartman and Sinclair, 1996), but stop at full seed set (R6) before leaves naturally brown. At later plant growth stages, the fungus may also cause symptoms on petioles, stems, and pods (Hartman et al., 2009). The symptomatic area increases significantly with time and physiological maturity of soybean plants (Levy et al., 1990). 

Visually inspect soybean plants throughout the survey site for symptoms focusing on areas of the field with high humidity (low areas of the field, densely planted areas) or areas that are showing foliar symptoms of disease or premature defoliation. Since C. glycines is not wind- or seed-borne, we expect an uneven distribution of the pathogen in early-infested fields, with local spread via rain-splashed spores over time. If present, surveyors should preferably collect severely infected green leaves to maximize the chance of identification.

Surveys should take place in soybean fields, especially in regions with high rainfall or humidity. If possible, select fields that have not been treated with fungicides. 

Conduct visual inspections of as many soybean plants as is practical, attempting to cover the entire field/survey area. Pay special attention to areas prone to water accumulation.

Collect symptomatic leaves with petioles. Store samples in the refrigerator or a cooler with a cold pack. Do not freeze samples.   

Datnoff, L., C. Levy, D. Naik, and J. Sinclair. 1986. Dactuliophora glycines, a sclerotial state of Pyrenochaeta glycines. Transactions of the British Mycological Society 87(2):297-301.

Hartman, G. L., L. E. Datnoff, C. Levy, J. B. Sinclair, D. L. Cole, and F. Javaheri. 1987. Red leaf blotch of soybeans. Plant Disease 71(2):113-118.

During the early stages of infection, the disease may be confused with Alternaria leaf spot, brown spot, or target spot (Hartman et al., 2009). The causal agent of these diseases (Alternaria alternata, Septoria glycines and Corynespora cassiicola) are present in the United States (WPFUS, 2025). All start as little brown lesions or spots, but these additional symptoms differentiate them (Hartman et al., 2015):

Alternaria alternata: Spots have concentric rings.

Septoria glycines: Lesions are irregularly shaped and often surrounded by yellow halos.

Corynespora cassiicola: Lesions are round to irregularly shaped, particularly along leaf margins, frequently surrounded by dull-green or yellowish-green halos, and larger spots are often distinctly zonate (marked with zones). 

To avoid collecting above-mentioned native species, surveyors should look for C. glycines blotches, pycnidia and sclerotia (Hartman and Murithi, 2019).