Individual lesions may grow together to form larger lesions. This fungus needs a hot, humid growing season to develop and does not appear every year even in susceptible varieties. Symptoms on the leaves include the characteristic lesions described above. Lesions on the stems are elongated and turn from a reddish color to a blackish color. Lesions on the pods are similar to leaf lesions.
Severe infection can cause premature defoliation.
There are many races of the frogeye fungus. Fortunately, there are also several sources of genetic resistance to the fungus. Most of the current varieties have a degree of resistance to this disease. Only healthy, disease-free seed should be planted. Rotation of soybeans with a non-susceptible crop or plowing under of crop residues can reduce inoculum potential.