Tobacco

State-of-the-art facilities have been established at Southern Piedmont AREC to conduct curing research with burley, dark air-cured and fire-cured, and flue-cured tobacco. Twelve specialized fire-cured barns were constructed in 2008. These barns have excellent control of curing parameters and are equipped with real-time temperature and relative humidity monitoring and data logging capability.

Five small-scale flue-cured barns were donated and have been upgraded with power inverters to allow for precise airflow control within the barns. A relative humidity sensor developed by Suretrol is being evaluated for use in flue-cured barns as an alternative to wet-bulb thermometers.

A solar-assisted flue-cured barn has been evaluated in an on-farm trial. Comparisons to the conventional barn show increased curing efficiency resulting from preheated air entering the curing chamber.

Black Shank

Black shank is caused by a fungal pathogen that lives in the soil and attacks tobacco roots and stalks. Widespread continuous planting of flue-cured tobacco cultivars possessing single-gene (designated Ph) resistance to black shank enabled tobacco producers to dramatically reduce the application of soil fungicides beginning in 1996. However, this has led to the breakdown in the efficacy of this resistance by shifting the distribution of the pathogen populations from host race 0 to race 1.

Granville (Bacterial) wilt

Granville (Bacterial) wilt is caused by a soil-inhabiting bacterium that invades tobacco plants through one or more roots, and often kills the entire plant. The pathogen can also invade tobacco plants through wounds, so early and shallow cultivation and hand-topping can help reduce spread in infested fields. Although symptoms are somewhat similar to those for black shank, intermediate symptoms of Granville wilt involve wilting on only one side, and wilted leaves may retain their normal green color rather than yellow. 

Tobacco Cyst Nematode

Tobacco cyst nematodes (TCN) are microscopic worms that live in the soil and feed on tobacco roots. TCN populations are thought to be decreasing in some fields due to the widespread planting of flue-cured cultivars with the Ph gene. Nematicide tests are conducted annually to evaluate their influence on nematode reproduction and tobacco yield and quality. TCN-resistant cultivars are also evaluated for their potential.

Tobacco Mosaic Virus

The tobacco mosaic virus (TMV) is the most widely distributed virus that affects tobacco crops. TMV can be spread by contaminated clippings mowers in the greenhouse, from tobacco roots and stalks remaining in the soil from previous crops, from weed hosts such as horsenettle and ground cherry, and contaminated objects and surfaces such as trays and sheets, and from manufactured tobacco products. Mosaic-resistant cultivars can reduce damage and may help reduce residual viruses in infested fields. If a TMV-resistant cultivar is planted, the entire field should be planted to the resistant cultivar.

Greenhouse culture has become the standard for transplant production with tobacco producers in Virginia. The use of greenhouse-grown transplants is advantageous for numerous reasons. Labor required for transplant production and for transplanting is dramatically reduced compared to the use of bare root transplants. Crop growth in the field tends to be much more uniform resulting in easier cultivation and fewer trips through the field when topping. The resulting tobacco crops tend to grow off and come into top more uniformly which will often carry over into maturation and ripening of the leaves.

Sanitation, ventilation and air circulation, temperature control, media and tray filling, fertilization, water quality, and clipping are important greenhouse management practices.

Aphids

The tobacco or green peach aphid has been the most severe insect pest of tobacco in Virginia. Aphid populations increase rapidly, doubling in size about every two days under favorable conditions. High populations of aphids can reduce tobacco yield by 5% to 25% or more. Aphids excrete honeydew as they feed which contains the excess sugars from the plant sap. This sticky, shiny honeydew is deposited on the leaves below the feeding aphids.  A dark, sooty mold often grows on the honeydew which gives the leaves a dark tint.  The combination of sooty mold and honeydew interferes with curing, reduces leaf quality, and often remains on tobacco after aphids have been controlled. Aphids are most severe on tobacco from late June to September.

Hornworms

Tobacco and tomato hornworms are large caterpillars (up to 4 inches long) that eat large amounts of tobacco leaf. Infestations may develop anytime from transplanting until harvest, but damage is usually most severe during August and September. Parasitized hornworms with the white egg-like cocoons of the parasitic wasp, Cotesia congregate, on their backs and eat much less than healthy hornworms. Predators also kill large numbers of hornworm larvae that are less than one inch long.Tobacco Budworms

Tobacco Budworms

Tobacco budworms feed in the buds of young tobacco plants causing many holes in the tiny developing leaves. These feeding holes become larger as the leaves grow which give the plants a ragged, distorted appearance. Tobacco plants usually compensate for this damage so yield and quality may not be affected. However, budworms sometimes top the plants prematurely causing early sucker growth that may stunt the plants and require extra labor to remove the suckers.

• 2024 Flue-Cured Tobacco Production Guide