Update on Tobacco Blue Mold: Spread Continues, Scout Fields Now

Tobacco blue mold has now been identified in southern Virginia as well as Pennsylvania; this is an additional range expansion over last week’s identification in eastern Tennessee. Dr. Chuck Johnson, plant pathologist specializing in tobacco in Virginia, reports that the majority of blue mold lesions were occurring on lower stalk leaves (lugs and cutters), but a few lesions had spread to the true leaf.

Scout Fields for Blue Mold

Kentucky growers, especially those located in the central and eastern parts of the Commonwealth, are encouraged to thoroughly scout their fields for blue mold. Scouting should be focused in areas with extended periods of leaf wetness. The longer a tobacco crop goes without being infected, the less yield-limiting blue mold will be. Tobacco that is nearing topping becomes less susceptible to the blue mold pathogen; thus, later-set crops are at highest risk of significant reductions in yield.

With continued rainy conditions forecasted for the rest of this week and a number of later-set crops, blue mold threatens to limit yields this year for a number of tobacco growers. If you suspect blue mold in your crop, contact your county Extension agent immediately for confirmation and recommendations.

Figure 2: Blue-gray sporulation of the blue mold pathogen on the underside of burley tobacco leaves (Photo: Chuck Johnson, Virginia Tech).

Figure 1: Blue-gray sporulation of the blue mold pathogen on the underside of burley tobacco leaves (Photo: Chuck Johnson, Virginia Tech).

Foliar Fungicides

Foliar fungicide sprays are critical to managing blue mold effectively, and growers are encouraged to consider spraying preventatively now. Recommended fungicides include Revus or Forum, Quadris, Orondis Ultra (if Orondis Gold has not already been used), Actigard, Aliette, and Manzate. Tobacco growers should take crop maturity and any contract restrictions into account prior to using Manzate in the field. Organic tobacco growers may consider Oxidate and Regalia as options for blue mold management, but data are scarce and efficacy will likely rely on frequent applications. Dr. Johnson from Virginia Tech suggests that crops that have fairly recently (within the past week) been treated with Quadris should have some kick-back activity from that application. However, only leaves that were physically impacted by Quadris would be protected; new or missed leaves would not be expected to be protected.

Additional Information

  • 2016 Fungicide Guide For Burley And Dark Tobacco (PPFS-AG-T-08)
  • Burley and Dark Tobacco Production Guide (ID-190)
  • Maintaining The Efficacy of Foliar Fungicides for Tobacco Disease Management (PPFS-AG-T-05)

 

By Emily Pfeufer, Extension Plant Pathologist

 

 

Posted in Tobacco