October 28, 2009

With harvest nearing completion, high humidity levels caused by an exceptionally moist year could potentially cause curing problems for growers of burley and dark tobacco, said specialists with the University of Kentucky College of Agriculture.

Much of the early-cured burley and dark air-cured crops are showing signs of houseburn or barn rot.

Andy Bailey, UK dark tobacco extension specialist, estimated that as much as two-thirds of the dark air-cured tobacco crop has at least small traces of the rot, which is also called "sweat." Barn rot can cause leaves to fall off the stalk, cause significant leaf weight reductions, and increased levels of undesirable chemical constituents in the cured leaf.

While barn rot is widespread, its levels are small enough on most dark air-cured crops that it should not pose quality problems at the receiving stations.

"A lot of the companies understand what our growing season has been like, and they expect to see some of that," Bailey said. "Unless there's a major problem, there should not be a major price reduction based on a single year situation."

However, growers will want to spend more time with damaged crops in market preparation.  If only a small percentage of the crop is showing signs of rot, growers should separate out leaves that have significant barn rot prior to delivery whether they have burley or dark tobacco. Growers need to have the barn doors open as much as possible to help remove the moisture from the crop.

"Unfortunately, there are no sprays or powders that are effective at stopping rots or molds in the barn," said Bob Pearce, UK extension burley tobacco specialist. "Using any product off-label in the barn could lead to unacceptable residues on the cured leaf."

Dark air-cured growers may be able to apply some dry heat to help rid the crop of moisture. Using a dry wood that produces very little smoke, such as sycamore, growers can let fires burn for a day or two, repeating this process about every two weeks. Bailey said some dark tobacco growers are taking some of their crop down from the barn and placing it on scaffold wagons to allow more air movement through the tobacco as it finishes curing.

Dark fire-cured tobacco was not as affected by barn rot due to its more-controlled curing process and is of good quality. However, some of the dark fired, dark air and burley is muddy due to the crops being harvested in wet conditions. Growers will need to spend extra time removing mud from the crop in preparation for market. Dark tobacco needs to wilt some in the field before it's moved to the barn, but because of cloudy, wet weather throughout the harvest season, some of the tobacco was harvested before this stage was completed, resulting in leaf breakage and bruising, Bailey said.

In addition to the rot, burley and dark air-cured growers are dealing with heavy mold growth on their cured leaves. Growers need to contact their contract holder to determine how the company wants the moldy tobacco handled, Pearce said. Depending on the company and the percentage of moldy tobacco, growers may need to separate the moldy tobacco from the rest of the crop during stripping.

Patience is critical for growers during the curing process. The cooler temperatures of October and November cause much slower cure than the warmer weather of traditional curing months of August and September. Moldy tobacco may need to go through several drying cycles to keep the mold from spreading.

"Growers need to be patient," Pearce said. "Plant stems are not drying well. These sappy stems could add to moisture levels and promote mold growth.

Holding bales of tobacco with active mold for six to eight weeks could cause a significant loss in quality. Stripping and baling moldy tobacco close to the sale date could reduce quality problems related to moldy tobacco because the plants will deteriorate less in the barn than in bales, Pearce said. He encourages growers to hold off baling moldy tobacco as long as possible, but realizes that due to the late growing season, it may not be possible for all growers because of the availability of their migrant workers.

When moldy or muddy tobacco is taken down and stripped, the movement of the tobacco could release large amounts of dust and mold spores into the air potentially creating a health concern for workers. Tobacco growers and their workers may want to use N95 respirators approved by The National Institute for Occupational Safety and Health to protect themselves from airborne dusts and mold spores.

While the high humidity has caused concerns, it has given both the burley and dark air-cured tobacco crops really nice color, which is a quality improvement compared to the flashy colors of the last two years, which were both dry with low humidity.

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Writer: Katie Pratt, 859-257-8774

UK College of Agriculture, through its land-grant mission, reaches across the commonwealth with teaching, research and extension to enhance the lives of Kentuckians.


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