Blue mold , a fungal disease, decreases or destroys tobacco quality. Initially it was diagnosed in 1921 in tobacco plant beds in Georgia, and by 1931 it had found its way southward to Florida and northward to South Carolina, North Carolina, and Virginia. The mold enters the tobacco plant through the leaves or systemically through the soil. It is promoted by cool, damp, and rainy weather. By 1940 blue mold had become a serious and widespread plant bed problem in North Carolina, severely damaging the supply of regional tobacco plants and forcing farmers to transport plants from other states. This resulted in the spreading of blue mold, along with other diseases, throughout the flue-cured and burley tobacco areas of North Carolina.
By the late 1970s blue mold had spread from plant beds into tobacco fields, costing farmers in North Carolina and other states over $252 million in lost market value. Scientific research during the last years of the twentieth century, however, proved reasonably successful in controlling the disease and the damage it causes.
Furney A. Todd, Tobacco in the United States (rev. ed., 1979).
Blue Mold Factsheet, NCSU Department of Plant Pathology: http://www.cals.ncsu.edu/plantpath/extension/fact_sheets/Tobacco_-_Blue_Mold.htm 
1947 research on controlling blue mold in Annual Report of North Carolina Agricultural Experiment Station  (p. 40) from NCDCR Digital Collections 
1 January 2006 | Yeargin, W. W.