Tobacco Blue Mold Confirmed in NC
Tobacco blue mold was confirmed (July 11, 2017) in commercial tobacco in Caswell County, North Carolina by the Plant Disease and Insect Clinic at NCSU.
Symptoms were consistent with blue mold, including chlorotic lesions on the tobacco leaf and bluish-gray sporangiospores on the underside of the lesions (Fig 1). Structures of Peronospora tabacina were found on leaves using microscopy (Fig 2).
Growers in this region should scout for symptoms. Risk of new infections decreases significantly after topping, but infection may still occur. If disease is present, an application of a fungicide with oomycete activity, such as Quadris, Revus, Forum, or Presidio, may help reduce disease. To see rates of fungicides, the 2017 North Carolina Agricultural Chemicals Manual has recommendations for blue mold control
Presently, this is an isolated field, and the disease is favored by cool, wet weather. If you suspect a blue mold infection, contact your county extension agent or submit a sample to the Plant Disease and Insect Clinic for confirmation.