Brown Stem Rot

Brown Stem Rot

The first report of brown stem rot came from Illinois in 1944. Since that time it has increased in incidence throughout the soybean production areas of the United States, primarily in the mid west. One reason for the increased incidence of brown stem rot is the shift to shorter rotations between soybeans and corn. The disease is caused by the fungus Phialophora gregata (Allington & D.W. Chamberlain) W.Gams = Cephalosporium gregatum Allington & D.W. Chamberlain. The fungus produces three wilt-inducing toxins known as gregatin A, C, and D. Isolates of the fungus have been divided into two types based on their ability to incite leaf symptoms. The type of leaf symptoms expressed include chlorosis, necrosis and wilting. Type I isolates cause these symptoms and type II isolates do not. In addition to soybean, mung and adzuki beans have also been identified as hosts of the pathogen. The fungus overwinters on buried soybean debris. Mycelium contained in the residue sporulates profusely on the debris and spores (conidia) server as inoculum. Fungal mycelia invade the main and lateral roots. Roots may be heavily colonized and the fungus moves up the plant via the xylem. Progression up the plant may be slow until the flowering when plant susceptibility is increases. Mycelium and spores present in the xylem may also invade the pith at this time. The disease is favored by cool temperatures and development is arrested at temperatures greater than 27^oC.

Symptoms

The most common symptom of this disease is a brown discoloration of the vascular tissue and pith. The extent of the discoloration is dependent on the physiological age of the host and the temperature. Initially the discoloration my only be evident at the nodes but becomes continuous throughout the stem as the plant ages and cool temperatures prevail. External stem symptoms are not visible until late in the growing season. At this time, the lower stem takes on a dull brown color. Wilting and premature defoliation and lodging may also occur and result in significant yield loss. These symptoms are heightened when infected plants are subjected to drought stress. Leaf symptoms produced by type I isolates consist of interveinal necrosis except for a narrow green border of healthy tissue around the vein.

Plant Health Management

Resistant Cultivars

Crop Rotation.

A three year rotation to a non host crop such as corn is recommended. Alfalfa and red clover should not be used in the rotation.

References

Mengistu, A., and Grau, C.R. 1986. Variation in morphological, cultural, and pathological characteristics of Phialophora gregata and Acremonium sp. recovered from soybean in Wisconsin. Plant Disease 70:1005-1009.

Nyvall, R.F. 1989. Field crop diseases handbook, 2^nd ed. Van Nostrand Reinhold New York, NY. 817 pp.

Sinclair, J.B. and P.A. Backman, eds. 1989. Compendium of soybean diseases, 3^rd ed. American Phytopathological Society, St. Paul, MN. 106 pp.

Useful Links

Purdue University

Caveat

This description is presented for information only and no endorsement is intented for products listed, nor criticism meant for products not mentioned. Always consult the product label before purchasing and using any pesticide.

Material contained on the Links from the page are the responsibility of the linked page's author(s).

This page was drafted by: Jane Christensen, Department of Plant Pathology, University of Nebraska-Lincoln

Disease images were provided by: Dr. David Wysong, Department of Plant Pathology, University of Nebraska-Lincoln

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This page is authored and maintained by:
Dr. J.E. Partridge, Department of Plant Pathology, University of Nebraska-Lincoln

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