Steve Bost | UT Extension Plant Pathologist | June 17, 2015
Blue mold was found in Maury County, TN yesterday by Extension agent Richard Groce in a 1½ acre field of 1-ft tall burley. The lesions were throughout the field and a second cycle of infections appeared to be beginning. This and the Greeneville greenhouse incident are the only reports of blue mold this year. All tobacco growers in the state should be advised to inspect their fields carefully, considering the uncertain source of these infestations and the disparate nature of their occurrence. A protective application of fungicides would be prudent for Middle TN and probably for points east also, especially considering the west-to-east direction of air flow with showers expected this week from tropical storm Bill.
Greenhouses still in operation should continue weekly applications of Manzate ProStik. In fields, Actigard is a plant resistance activator effective against blue mold, but plant height must be considered. Minimum plant heights for the use of Actigard are 12 inches for dark tobacco and 18 inches for burley. Quadris, Revus, Forum, and Presidio are fungicides that must be incorporated into resistance management programs by alternating with fungicides with a different mode of action, “MOA.” (Of these, only Revus and Forum are from the same MOA group, Group 40). In addition, Forum and Presidio must be tank mixed with a different MOA. Manzate is the only blue mold fungicide that is not subject to resistance and thus makes a good alternation or tank mix partner if it is not prohibited by the contract or discouraged by the buyer. The weather pattern will determine the need for follow-up sprays.
Let your local Agronomist or Extension Agent know if you see blue mold or suspect it.