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Significance

Historical Significance
In 1892, Peter Henry Rolfs first published a description of a new disease on tomato where some fields in Florida showed a greater than 70% loss. The fungus was named Sclerotium rolfsii by Saccardo in 1911. Descriptions of the disease in Connecticut, Louisiana, North Carolina, Japan, Ceylon, and India were published in the early 1900s. In 1928, the USDA reported that S. rolfsii and root-knot nematode caused more damage in southern states than any other pathogens. In the first half of the 20th century, peanut production sustained losses of 10-20 million dollars annually due to this disease. Losses of 25-50% were not uncommon in 1938-1947. By 1944, the disease was known to occur in 24 states (Figure 27). By 1966, there were almost 2000 publications on this disease in various locations around the world, but mostly from tropical and subtropical areas.

Figure 27

Current Significance
Sclerotium rolfsii continues to be a problem in a variety of crops when conditions are warm, humid and rainy. Today this disease occurs around the world in the equatorial zone between the 45º N and S latitudes. It is commonly found in the United States, Central America, the Carribbean area, South America, countries bordering the Mediterranean Sea, Africa, India, Japan, the Philippines, Hawaii, Australia, and New Zealand. Occasionally, southern blight has been reported in North China, Europe, and some northern areas of the United States, including Indiana, Illinois, and New York. There has been one report from Siberia. In the southern United States, S. rolfsii has been especially damaging on cotton in Arizona, on peanut and tomato in many areas of the Southeast, and on sugar beet in California. During the middle of the 20th century, this disease was controlled to some degree by fumigation or soil applied fungicides. These chemicals are often too expensive and too toxic for many situations, and future uses of fumigants are being restricted due to environmental concerns. Today, control of this fungus disease is still the subject of many research projects involving chemicals, biological agents, soil amendments, cultural modifications, disease physiology, nutrition studies, and cultivar/variety resistance. Despite these efforts, S. rolfsii, like many other soilborne fungal disease agents, continues to be a difficult pathogen to control.

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