Maintaining quality vital in stored tobacco

Flue-cured tobacco crops in south Georgia and north Florida have benefited greatly this year from timely rainfall and minimum disease pressure. As a result, most growers have produced all of their quota and some finished the season with excess production that must be stored.

“Growers will not be allowed to sell excess production due to the limited availability of non-produced quota,” says J. Michael Moore, University of Georgia Extension tobacco specialist. “Growers who hold this excess production until next season should manage the tobacco closely to maintain quality. Growers must take this responsibility seriously, and there's several things they can do to insure that quality is maintained.”

In general, says the agronomist, tobacco should be stored in a clean, dry, insect-free facility, such as a packhouse or bulk curing barn. “The costs of producing, harvesting and curing carryover tobacco already has been invested, and the carryover tobacco is additional profit for the producer if quality is maintained by proper storage,” he says.

Moore advises growers to store carryover tobacco in curing barns in boxes or in racks used for curing. “Barns are the most sanitary facilities on the farm at the end of the curing cycle, after the threat of insects has been eliminated. However, once the barn is opened and tobacco is moved in or out, new insect contamination may occur. The same thing may happen over time with the natural movement of insects.”

He also advises growers to avoid storing tobacco in compressed bales. Damage, Moore says, has resulted from tobacco being stored in areas with excessive moisture and from the combining of tobacco from multiple stalk positions. Tobacco which cannot be left in barns should be stored in sheets, and the tobacco should be dry throughout the sheet when placed in storage, he says.

“Care should be taken to provide good ventilation under and around the tobacco. Stack sheets no more than two sheets high on wooden pallets or rails, especially if the storage area floor is concrete, asphalt or near ground level. A vapor barrier of polyethylene or roofing paper placed on the floor will reduce the infiltration of moisture,” he says.

Growers should leave space to move the stacks around when making periodic checks every two to four weeks, notes Moore. If bulk curing barns are used, fans may be run occasionally to insure that tobacco remains dry, he says.

“Tobacco may be re-dried at temperatures not to exceed 100 degrees F. to avoid color changes and reductions in quality. Heat treating loosely packed dry tobacco at 140 degrees F. for one hour may be used to initially reduce the number of insects. However, no residual effect of the treatment should be expected. Tobacco may be re-infested by insects at a later date and may require re-treatment.”

It's important, says Moore, that growers avoid any possible insect contamination of carryover tobacco from old tobacco sheets, old stored tobacco, tobacco trash or other sources of food for insects.

Tobacco moths and the cigarette beetle commonly attack tobacco that is stored on the farm, he says. “The tobacco moth is the most serious of these insects. The larvae, which cause all of the damage, are pinkish to yellow to off-white caterpillars about one half inch long. They burrow into and form ragged holes in the cured leaves.

“Entire leaves may be consumed except for the midrib and large veins. The larvae also deposit webbing and fecal pellets on the infested tobacco. The adult tobacco moth is a small, gray moth about three eighths inch long with a five eighths inch wingspread.”

Cigarette beetles, says Moore, are light to dark brown hump-backed insects about one eighth inch long. Adults leave tiny holes as they emerge from pupae cases within the tobacco. The hairy C-shaped larvae, which cause most of the damage, are whitish with a brown head and are about one fifth inch long. They leave behind powdery waste which can give tobacco an unpleasant flavor.

Controlling established insect infestations is difficult, he says, so prevention is very important. The most important step in prevention, he adds, is sanitation.

“Before tobacco is placed in storage, prepare a clean storage area. Clean out and burn all tobacco and debris from the storage area. Plant trash remaining in the storage area might harbor insects that can move to the tobacco.”

To help prevent tobacco moth infestations, Moore recommends treating with Bacillus thuringiensis (Bt). “Apply a fine spray to loose tobacco as it is being sheeted. It's very hard to repack sheets and get the good coverage required. One suggestion might be to apply Bt as a fine mist as the tobacco is sent through a conditioning cylinder or tumbler.”

Stored tobacco should be checked every two to four weeks during the fall and winter for signs of insects and for new damage, he says. If tobacco moths are found, they should be treated with Bt.

“Treating the outside of piles and/or the sheets probably will not control an established infestation. Piles must be taken apart and the tobacco treated as loose leaves before re-sheeting. Sheets also may be treated.”

Malathion, says Moore, is labeled for the treatment of storage facilities as a residual spray for the control of cigarette beetles. There are no labeled cigarette beetle preventive insecticides for applying directly to tobacco.

If cigarette beetles are found in stored tobacco, the tobacco may be fumigated, he says. “Current regulations make it very difficult for farmers to legally fumigate on their own. Therefore, fumigation probably should be done by a professional. Some fumigants give an off-flavor to the tobacco and aren't recommended.”

Fumigation controls only those insects that are present, says Moore. It is not a preventive treatment. “Most fumigants can cause damage to metals, especially copper wiring in motors, when brought into contact at high concentrations. Do not treat stored tobacco with pesticides not labeled specifically for this purpose. Always read and follow label instructions.”

The safest and simplest method of eliminating insects in cured tobacco is through the use of heat in the curing barn, he says. “To simplify this process, tobacco which will be stored through the winter should be left in the curing barn in the curing racks or boxes. Regular inspection of the tobacco and the occasional use of the barn fan/or furnace will maintain low moisture content and reduce the potential for insect infestation.”

Producers should store only tobacco which has been cured in a barn with an indirect heat source, he says, as all tobacco will have to be certified as low nitrosamine in 2002. Store tobacco only in retrofitted barns to avoid exposure to exhaust gases when drying, he adds.

“Tobacco warehouses must be bonded and insured if they store tobacco belonging to more than one other person. Consider the effort required to manage stored tobacco that is not stored on the farm. Most warehouses have cement or asphalt floors, requiring tobacco to be stored on pallets to avoid moisture absorption.”

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