Blue mold is a downy mildew disease of tobacco

Tobacco

Tobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as a pesticide and, in the form of nicotine tartrate, used in some medicines...

 that is caused by Peronospora tabacina, a fungus-like protist in the family Peronosporaceae

Peronosporaceae

Peronosporaceae are a family of water moulds that contains 17 genera, comprising more than 600 species. Most of them are called downy mildews. The closest relative of Peronosporaceae is Phytophthora....

. Blue mold can cause severe damage to susceptible tobacco plants in many parts of the world. Since it is an obligate parasite, it must have living tobacco tissue in order to grow.

Although tobacco remains the primary host for this disease, other hosts including pepper plants and eggplants can also be reservoirs.

See also

• The term blue mold may also be applied to Penicillium roqueforti
  Penicillium roqueforti
  Penicillium roqueforti is a common saprotrophic fungus from the family Trichocomaceae. Widespread in nature, it can be isolated from soil, decaying organic matter, and plants. The major industrial use of this fungus is the production of blue cheeses, flavouring agents, antifungals, polysaccharides,...
  
  , a mold
  Mold
  Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are not considered to be microbes but microscopic fungi that grow as single cells called yeasts...
  
   used in producing the taste and characteristic blue-green inclusions in Roquefort and other blue cheese
  Blue cheese
  Blue cheese is a general classification of cow's milk, sheep's milk, or goat's milk cheeses that have had cultures of the mold Penicillium added so that the final product is spotted or veined throughout with blue, blue-gray or blue-green mold, and carries a distinct smell, either from that or...
  
  s.

• A powdery mildew disease of hops
  Hops
  Hops are the female flower clusters , of a hop species, Humulus lupulus. They are used primarily as a flavoring and stability agent in beer, to which they impart a bitter, tangy flavor, though hops are also used for various purposes in other beverages and herbal medicine...
  
   has sometimes been erroneously called blue mold. It is caused by Sphaerotheca
  Sphaerotheca (fungi)
  Sphaerotheca is a genus of ascomycete fungi that currently includes two plant pathogen species, Sphaerotheca epilobii and Sphaerotheca castagnei, that cause forms of Powdery mildew. The original type species, Sphaerotheca pannosa, now belongs to the genus Podosphaera....
  
   humuli, a fungus
  Fungus
  A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
  
   in the order Erysiphales
  Erysiphales
  Erysiphales are an order of ascomycete fungi. The order contains one family, Erysiphaceae. Many of them cause plant diseases called powdery mildew.-Systematics:The order contains one family , 28 genera and approximately 100 species...
  
  . This hops disease became epidemic in the New York state hops industry in 1909, ultimately leading to the abandonment of the crop in the Northeastern USA.