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dhensley@utk.edu
The blue mold threat currently 6/16/08 is low for Tennessee, however with expected afternoon showers, the threat could increase if any infected plants were transported into the area or if air currents flow up our way and deposit blue mold spores.
Tobacco blue mold was reported in Live Oak, Florida on 6/16/08. The tobacco in the reported field is at the stage of topping and is very tall and lush. Blue mold lesions were primarily on lower leaves, but in one or two foci, lesions were also seen in mid and upper canopy. Prior to the observation date (June 10), the grower had only applied mancozeb on one date.
Blue mold has been reported in Blackstone, VA on 6/09/08 by Chuck Johnson. Blue mold symptoms were first observed on Friday, June 6 on a volunteer tobacco plant in a 100 ft-long float-style tobacco greenhouse at the Southern Piedmont Center. Abundant lesions were also found on plants remaining in the greenhouse for replanting. Blue mold was confirmed on Monday morning, June 9, based on profuse sporulation on some older lesions. Sporulation was rarely observed on smaller and distinct lesions versus chlorotic areas arising from merged lesions. Young lesions may represent a 3rd or later pathogen generation.
Transplants in the greenhouse have not been sprayed with a fungicide but are currently being destroyed.
Weather was very mild and wet from early April through mid-to-late May. Very late May and early June have been dry, with extremely hot weather for the past week, around 100 since last Thursday or Friday and similar temperatures forecasted for Monday and Tuesday, June 9 and 10, and little chance of rain this week in theVirginia area.
Blue mold has been reported in two counties (Pierce and Lowndes Counties) in Southern Georgia on 6/04/08. The Blue Mold Forecast Center indicated that the blue mold in Georgia possibly originated from Cuba.
Blue mold has been identified in a plant bed in northern Florida,
near Alachua (Gainesville area). The infection likely originated from spores from infected
plants in Cuba. The infection was found early this week on 3/12/08.
Growers should not under any circumstances import transplants from
Florida or south Georgia. Our greenhouse producers need to be treating
their transplants with protectant fungicides as soon as the plants are
large enough. Dithane may be used, but unfortunately it is short
supply and may not be available for those who do not already have some on
hand. Alliette and streptomycin also have some blue mold activity, and may
be options, if Dithane is not available (PLEASE READ THE LABEL). Treatment can begin when emerged
transplants have leaves that are dime sized. See SP 91, Tobacco Pest
Control, for more information about the use of these materials.
With this early outbreak, it is likely we will be fighting blue mold
in the field early this year as well. Producers may want to be checking
supplies of Dithane, Forum, Acrobat, Quadris and Actigard, and thinking
about their control strategies.
Please let me (dhensley@utk.edu) know if you find blue mold or suspect it in your area. I will continue to
send information to county extension personnel, to keep you posted on the situation, and you can visit this
web page for regular updates on blue mold and other diseases.
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PRODUCTS AVAILABLE FOR BLUE MOLD CONTROL
Dithane DF, Acrobat 50WP, Forum, Aliette, Quadris, and Actigard are labeled for blue mold control.
Read the label prior to use.
If blue mold is present in the field, use protectant fungicides; Dithane DF, Acrobat MZ or Dithane DF mixed with Acrobat 50WP and use hollow cone nozzles directed over the row. Drop nozzles will be needed on larger plants to obtain thorough leaf coverage.
Actigard may be applied to tobacco 18 inches in height or larger, however it must be applied five days prior to the onset of infection to achieve control. Actigard does have advantages, because it may be applied with flat fan nozzles and coverage is not as critical as protectant type fungicides.
note: if you intend to use Acrobat 50WP or Forum, you must also use Dithane DF with the product to achieve optimum control.
If yellow leaf spots appear on tobacco leaves, please take them to your local county extension agent for positive identification.