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Anthracnose: Kentucky Soybean IPM

Anthracnose


Symptoms

Symptoms of anthracnose can develop in soybeans at any stage of crop development. Most commonly, however, symptoms appear in the early reproductive stages on stems, pods and leaf petioles as irregularly-shaped brown blotches.

Anthracnose on soybeans
Closeup of anthracnose Blotches are embedded with black fungal bodies which have small, but visible, spines. These structures can be seen with the unaided eye but may be visible more easily with a hand lens.

Foliage develops brown lesions on the veins and cankers on the leaf petioles. Leaves may roll and defoliate prematurely and plants may be stunted. Infected pods may be shrivelled and contain no seed; or more two-seeded pods, with shrivelled moldy seed, may be evident. Pods can be diseased and the seed may be infected, but symptoms are not always evident in the seed.

The irregularly shaped brown blotches caused by anthracnose may resemble pod and stem blight . Often, anthracnose and pod and stem blight occur together on the same plants late in the season.

Cause

Anthracnose is caused by Colletotrichum dematium var. truncatum and several related species, and varieties of the fungus Glomerella spp. The fungi survive between seasons in infested crop residue and seed.

Plants can become infected at any stage of development, but are especially susceptible during bloom and podfill. Development of anthracnose is favored during prolonged periods of wet weather. Anthracnose is evident to one degree or another every time soybeans are grown.

IPM Techniques

  • Examine plants every two weeks from beginning pod fill to harvest maturity for the presence of anthracnose.
    • At each site in the field examine two rows of plants 10 feet in length.
    • The number of sites you will need to check in each field is based on the field size.
    • To determine the number of scouting sites see the field size and number of locations chart.

  • Plant high-quality, disease-free seed or certified seed.

  • Rotating fields out of soybeans and plowing fields to bury the infested soybean residue will help in overall management of anthracnose.

References and Additional Information

  • IPM-3 Kentucky IPM Manual for Soybeans

  • PPA-10b Kentucky Plant Disease Management Guide for Soybean by D.E. Hershman, Extension Plant Pathologist

  • Compendium of Soybean Diseases, J.B. Sinclair and P. A. Backman (The American Phytopathological Society Press)

This site was created and is maintained by Pat Dillon, Department of Entomology, University of Kentucky, S-225 Agricultural Science Ctr North, Lexington, KY USA  40546-0091 (phone: 859/257-3571). Please send questions or suggestions to: pdillon@uky.edu