Southern stem blight or stem rot (Sclerotium rolfsii)

Sclerotium rolfsii causes southern blight, which is probably the most widespread and most important disease of vegetables in the south, inflicting economic damage on most vegetables. Although eventually all plant parts are affected, yellowing and wilting of leaves are often the first symptoms. As the disease develops, highly resistant sclerotia are produced on the stem near the soil line. Warm weather and high soil moisture, particularly following a dry spell, create favorable conditions for the development of southern blight.

A number of cultural practices may help to control southern blight:

• avoidance of heavily infested fields;
• burial of infected plant residues;
• long rotations to grasses and buckwheat;
• soil solarization for 4 to 6 weeks at 100 degrees F to 120 degrees F;
• deep plowing just before planting;
• reduced cultivation after planting; and
• weed control (preferably without cultivation).

In studies in the North Carolina coastal plain in which solarization was combined with the introduction of the disease-suppressing organism Gliocladium virens, disease incidence was reduced by 49 percent right after solarization and by 60 percent in the season following treatment. Gliocladium appeared to offer additional protection in years when solarization was not effective because temperatures were too low.

References

Jenkins, S.F. and C.W. Averre. 1986. Problems and progress in integrated control of southern blight of vegetables. Plant Disease 70:614-619.

Ristaino, J.B., K.B. Perry and R.D. Lumsden. 1991. Effect of solarization and Gliocladium virens on sclerotia of Sclerotium rolfsii, soil microbiota, and the incidence of southern blight of tomato. Phytopathology 91:1117-1124.