It is an elusive and explosive disease of the tobacco plant at all stages of production. More than any other disease of burley tobacco, blue mold is capable of impacting supplies over a large area with little warning. However, in most years the activity of blue mold is very limited, but it causes significant concern in those communities where it does occur. Burley tobacco is especially susceptible because of inherent genetic susceptibility, conducive environmental conditions in the production area, and a production system that favors disease development. Currently, the greatest threat to the tobacco industry from blue mold is from metalaxyl-insensitive strains.
Blue mold is caused by an airborne fungus.
The fungus survives and reproduces only on live tobacco, based on all available research to date. The main source of the pathogen for Kentucky appears to be windborne spores blown into the state from points south. Because of this, Kentucky participates in the North American Blue Mold Warning System in order to remain informed about the status of blue mold as the disease develops along various routes into the state. Another important source of the disease is infected transplants. The fungus can over-winter in Kentucky on live tobacco plants in greenhouses and probably during mild winters even on live tobacco plants that survive the winter in the field.