North Carolina Plant Disease and Insect Clinic
Plant Disease Fact Sheets

Southern stem rot of peanut

Figure 1. Signs and symptoms of Southern stem rot on peanut

Figure 2. Tan sclerotia produced by the southern stem rot fungus

Figure 3. Below ground damage due to southern stem rot. Note the white mycellium and sclerotia of the fungus.

Barbara Shew

Updated June 17, 2011

Southern stem rot of peanut is caused by the soil borne fungus Sclerotium rolfsii. The disease is also known as stem rot or white mold on peanut and as southern blight on vegetables. Southern stem rot and S. rolfsii  are very common and can be found in most peanut fields in North Carolina. Damage ranges from mild to severe.

Symptoms and signs

Symptoms of southern stem rot include wilting of individual stems, stem lesions, shredded stems and pegs, rotted pods, and plant death. Stem lesions and pods are similar in color to a brown paper bag. Coarse white strands of the fungus growing in a fan-shaped pattern may be present on lower stems, leaf litter, or soil (Figure 1). Later, tan to brown sclerotia that look like mustard seed may be present (Figure 2). The signs of the fungus are diagnostic of southern stem rot, but damage can occur even when these signs are absent. (video)

Conditions that favor the disease

Fields with heavy vine growth and high moisture are most prone to stem rot. This disease is most active during the hottest part of the season, especially following rain. In drier seasons, the fungus is most active underground, causing stem and pod damage that may not be noticeable until digging (Figure 3). Southern stem rot often is found together with CBR.

Cultural Control

Sclerotium rolfsii has an extremely broad host range, but it does not attack small grains, corn, and other grass species. Rotations with these crops will help to reduce stem rot problems. Avoid rotations with soybeans, tobacco, melons, and vegetables.

The virginia-type cultivar Bailey (and possibly Sugg) has good partial resistance to southern stem rot. All other virginia-type cultivars are susceptible or highly susceptible.

Chemical Control

Some fungicides used to control leaf spots also control southern stem rot. Using a soil fungicide as part of a leaf spot control program is beneficial in most fields. Examples include azoxystrobin (Abound), pyraclostrobin (Headline), tebuconazole (Folicur and generic brands), and prothioconazole + tebuconazole (Provost).  However, control may require higher rates than those used for leaf spot control. Flutolanil (Convoy or Artisan) controls southern stem rot but not foliar diseases, so a leaf spot control program is necessary with this fungicide. See the North Carolina Agricultural Chemicals Manual for labeled fungicides and rates.

Most soil fungicides work best when applied just before disease onset. Make at least 2 applications of a soil fungicide according to the leaf spot advisory or calendar schedule between July 15 and the end of August. High spray volumes (20 gal/a) and spraying when leaves are folded (before dawn) can increase fungicide deposition on stems but may make foliar disease control less effective.

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