Southern Stem Rot on Peanut

Written by Barbara Shew 

The fungus Sclerotium rolfsii has over one thousand plant hosts and causes diseases on field, vegetable, and ornamental crops grown in North Carolina. On many hosts, the first sign of infection are profuse strands of white, fan-shaped fungal growth at the base of the plant. Later, the fungus produces large numbers of round, tan-to-brown sclerotia that resemble mustard seed.

Stem Rot on Peanut ( Photo: B. Shew)

On peanut, the disease caused by S. rolfsii is known as southern stem rot, stem rot, or white mold. White fungus growth appears when the environment is right, often just following a rain (Figure 1). However, southern stem rot can be very damaging on peanut even when the distinctive fungus is not apparent; the damage often is hidden below ground. In addition, above-ground symptoms of stem rot can be hard to distinguish from other important peanut diseases, including CBR, Sclerotinia blight, and Rhizoctonia limb rot. The best way to determine the severity of a stem rot problem is to check the plants within an hour or two of digging. It is a good idea to check peanuts for symptoms of stem rot, CBR, and nematode damage immediately after digging. Growers should note problem areas so that appropriate controls can be used the next time peanuts are grown. I prepared a short video pointing out the distinctive features of stem rot on freshly dug peanut plants.



For more information about peanut diseases and their control, check out these links:
http://www.cals.ncsu.edu/plantpath/extension/clinic/fact_sheets/index.php?do=plant&id=1
http://www.peanut.ncsu.edu/